mtd: spi-nor: sort headers alphabetically

Sorting headers alphabetically helps locating duplicates,
and makes it easier to figure out where to insert new headers.

Signed-off-by: Tudor Ambarus <tudor.ambarus@linaro.org>
Reviewed-by: Pratyush Yadav <pratyush@kernel.org>
Signed-off-by: Pratyush Yadav <pratyush@kernel.org>
Link: https://lore.kernel.org/r/20250211-spi-nor-guard-mutex-v1-1-05ed77a484d9@linaro.org