Fix: Only use a single transmit buffer when transmitting OpenCyphal/CAN frames.

[aentinger]

See https://forum.opencyphal.org/t/uavcan-can-tx-buffer-management-in-can-fd-controllers/1215 .

[github-actions]

Memory usage change @ 575ad6b

Board	flash	%	RAM for global variables	%
arduino:mbed_edge:edge_control	💚 -64 - 0	-0.01 - 0.0	0 - 0	0.0 - 0.0
arduino:mbed_nano:nano33ble	💚 -64 - 0	-0.01 - 0.0	0 - 0	0.0 - 0.0
arduino:mbed_nano:nanorp2040connect	💚 -66 - 0	-0.0 - 0.0	0 - 0	0.0 - 0.0
arduino:mbed_portenta:envie_m4	💚 -64 - 0	-0.01 - 0.0	0 - 0	0.0 - 0.0
arduino:mbed_portenta:envie_m7	0 - 0	0.0 - 0.0	0 - 0	0.0 - 0.0
arduino:samd:mkr1000	💚 -68 - 0	-0.03 - 0.0	0 - 0	0.0 - 0.0
arduino:samd:mkrfox1200	💚 -68 - 0	-0.03 - 0.0	0 - 0	0.0 - 0.0
arduino:samd:mkrgsm1400	💚 -68 - 0	-0.03 - 0.0	0 - 0	0.0 - 0.0
arduino:samd:mkrnb1500	💚 -68 - 0	-0.03 - 0.0	0 - 0	0.0 - 0.0
arduino:samd:mkrvidor4000	💚 -68 - 0	-0.03 - 0.0	0 - 0	0.0 - 0.0
arduino:samd:mkrwan1300	💚 -68 - 0	-0.03 - 0.0	0 - 0	0.0 - 0.0
arduino:samd:mkrwan1310	💚 -68 - 0	-0.03 - 0.0	0 - 0	0.0 - 0.0
arduino:samd:mkrwifi1010	💚 -68 - 0	-0.03 - 0.0	0 - 0	0.0 - 0.0
arduino:samd:mkrzero	💚 -68 - 0	-0.03 - 0.0	0 - 0	0.0 - 0.0
esp32:esp32:esp32	💚 -64 - 0	-0.0 - 0.0	0 - 0	0.0 - 0.0
rp2040:rp2040:rpipico	💚 -72 - 0	-0.0 - 0.0	0 - 0	0.0 - 0.0

Click for full report table

Board	examples/MCP2515-CAN-Sniffer flash	%	examples/MCP2515-CAN-Sniffer RAM for global variables	%	examples/MCP2515-Loopback flash	%	examples/MCP2515-Loopback RAM for global variables	%
arduino:mbed_edge:edge_control	0	0.0	0	0.0	-64	-0.01	0	0.0
arduino:mbed_nano:nano33ble	0	0.0	0	0.0	-64	-0.01	0	0.0
arduino:mbed_nano:nanorp2040connect	0	0.0	0	0.0	-66	-0.0	0	0.0
arduino:mbed_portenta:envie_m4	0	0.0	0	0.0	-64	-0.01	0	0.0
arduino:mbed_portenta:envie_m7	0	0.0	0	0.0	0	0.0	0	0.0
arduino:samd:mkr1000	0	0.0	0	0.0	-68	-0.03	0	0.0
arduino:samd:mkrfox1200	0	0.0	0	0.0	-68	-0.03	0	0.0
arduino:samd:mkrgsm1400	0	0.0	0	0.0	-68	-0.03	0	0.0
arduino:samd:mkrnb1500	0	0.0	0	0.0	-68	-0.03	0	0.0
arduino:samd:mkrvidor4000	0	0.0	0	0.0	-68	-0.03	0	0.0
arduino:samd:mkrwan1300	0	0.0	0	0.0	-68	-0.03	0	0.0
arduino:samd:mkrwan1310	0	0.0	0	0.0	-68	-0.03	0	0.0
arduino:samd:mkrwifi1010	0	0.0	0	0.0	-68	-0.03	0	0.0
arduino:samd:mkrzero	0	0.0	0	0.0	-68	-0.03	0	0.0
esp32:esp32:esp32	0	0.0	0	0.0	-64	-0.0	0	0.0
rp2040:rp2040:rpipico	0	0.0	0	0.0	-72	-0.0	0	0.0

Click for full report CSV

Board,examples/MCP2515-CAN-Sniffer<br>flash,%,examples/MCP2515-CAN-Sniffer<br>RAM for global variables,%,examples/MCP2515-Loopback<br>flash,%,examples/MCP2515-Loopback<br>RAM for global variables,%
arduino:mbed_edge:edge_control,0,0.0,0,0.0,-64,-0.01,0,0.0
arduino:mbed_nano:nano33ble,0,0.0,0,0.0,-64,-0.01,0,0.0
arduino:mbed_nano:nanorp2040connect,0,0.0,0,0.0,-66,-0.0,0,0.0
arduino:mbed_portenta:envie_m4,0,0.0,0,0.0,-64,-0.01,0,0.0
arduino:mbed_portenta:envie_m7,0,0.0,0,0.0,0,0.0,0,0.0
arduino:samd:mkr1000,0,0.0,0,0.0,-68,-0.03,0,0.0
arduino:samd:mkrfox1200,0,0.0,0,0.0,-68,-0.03,0,0.0
arduino:samd:mkrgsm1400,0,0.0,0,0.0,-68,-0.03,0,0.0
arduino:samd:mkrnb1500,0,0.0,0,0.0,-68,-0.03,0,0.0
arduino:samd:mkrvidor4000,0,0.0,0,0.0,-68,-0.03,0,0.0
arduino:samd:mkrwan1300,0,0.0,0,0.0,-68,-0.03,0,0.0
arduino:samd:mkrwan1310,0,0.0,0,0.0,-68,-0.03,0,0.0
arduino:samd:mkrwifi1010,0,0.0,0,0.0,-68,-0.03,0,0.0
arduino:samd:mkrzero,0,0.0,0,0.0,-68,-0.03,0,0.0
esp32:esp32:esp32,0,0.0,0,0.0,-64,-0.0,0,0.0
rp2040:rp2040:rpipico,0,0.0,0,0.0,-72,-0.0,0,0.0