Added an internal function to obtain the flash page layout in
run-length encoded format. The API is simple and allows the actual
public API implementations to be simple and maintainable.
This feature can be enabled by using the FLASH_PAGE_LAYOUT Kconfig
option. This API is required for the implementation of flash file
system.
Added a public API to get flash page information (size and start offset)
by offset within the flash and by index of the page.
Added a generic implementation of the internal flash_get_page_info API.
Added an additional public API call to get the total count of pages in
the flash memory and its generic implementation.
Signed-off-by: Andrzej Puzdrowski <andrzej.puzdrowski@nordicsemi.no>