Remove redundant register count check

We have the same check already in exported functions modbus_read_registers
and modbus_read_input_registers which both calls out to the internal
static function read_registers.

So we can safely remove this redundant check in read_registers.

Signed-off-by: Michael Heimpold <mhei@heimpold.de>

src/modbus.c

@@ -1146,16 +1146,6 @@ static int read_registers(modbus_t *ctx, int function, int addr, int nb,
     uint8_t req[_MIN_REQ_LENGTH];
     uint8_t rsp[MAX_MESSAGE_LENGTH];
 
-    if (nb > MODBUS_MAX_READ_REGISTERS) {
-        if (ctx->debug) {
-            fprintf(stderr,
-                    "ERROR Too many registers requested (%d > %d)\n",
-                    nb, MODBUS_MAX_READ_REGISTERS);
-        }
-        errno = EMBMDATA;
-        return -1;
-    }
-
     req_length = ctx->backend->build_request_basis(ctx, function, addr, nb, req);
 
     rc = send_msg(ctx, req, req_length);