drivers/mtd_spi_eeprom: add MTD wrapper for AT25XXX EEPROMs

[JokoMLPA]

Contribution description

Adding mtd wrapper for SPI-EEPROMs like at25xxx or M95xxx using mtd interface.
The structure is similar to mtd_flashpage or mtd_sdcard.

Testing procedure

You can test the driver using RIOT/examples/filesystem (via littlefs). You need to define MTD0 in your board.h and create a mtd_spi_eeprom_t configuration containing the driver parameters, which has to be passed to the mtd layer.

Issues/PRs references

[roberthartung]

It looks like there are many unrelated changes, am I correct here? I would like to see the base implementation + tests in one PR and then changes to the boards if needed.

[benpicco]

@JokoMLPA please do a git rebase -i master and remove all the unrelated commits.

Alternatively, since this is only one commit, you can also do a git reset --hard master and then curl https://github.com/RIOT-OS/RIOT/commit/b1ce9f4b9e19a606a3c548407762c8814bc42dc7.patch | git am

git cherry-pick b1ce9f4b9e19a606a3c548407762c8814bc42dc7 should also work

[benpicco]

Can you please also add a simple test application to tests/ so this can be compile-tested by CI?

[benpicco]

Travis has some more nits and Murdock isn't happy yet.

[benpicco]

Works like a charm - tested with examples/filesystem (requires #14006).

One more thing - can you please add this patch:

--- a/drivers/Makefile.dep
+++ b/drivers/Makefile.dep
@@ -509,6 +509,10 @@ endif
 ifneq (,$(filter mtd_%,$(USEMODULE)))
   USEMODULE += mtd
 
+  ifneq (,$(filter mtd_at25xxx,$(USEMODULE)))
+    USEMODULE += at25xxx
+  endif
+
   ifneq (,$(filter mtd_sdcard,$(USEMODULE)))
     USEMODULE += sdcard_spi
   endif

So all the user has to do is USEMODULE += mtd_at25xxx and then dependencies will be resolved automatically.

[benpicco]

Please squash!

[maribu]

Nitpick: Add a colon to the commit message after the subsystem (drivers/at25xxx: add MTD wrapper for AT25XXX EEPROMs).