spi_flash_read and spi_flash_write currently have a limitation that source and destination must be word-aligned.
This can be fixed by adding code paths for various unaligned scenarios, but function signatures also need to be adjusted.
As a first step (since we are pre-1.0 and can still change function signatures) alignment checks are added, and pointer types are relaxed to uint8_t.
Later we will add handling of unaligned operations.
This change also introduces spi_flash_erase_range and spi_flash_get_chip_size functions.
We probably need something like spi_flash_chip_size_detect which will detect actual chip size.
This is to allow single application binary to be used on a variety of boards and modules.
