drivers: spi_nor: improve documentation and validation on flash layout size

The smallest region that can be erashed is one sector, so setting
SPI_NOR_FLASH_LAYOUT_PAGE_SIZE=2048 will fail at runtime when the
flash page API is used to erase a single (or misaligned) page.  Add a
compile-time check that the requested layout page size is erasable.

Signed-off-by: Peter A. Bigot <pab@pabigot.com>
2 files changed