fs: littlefs: use uintptr_t instead of int for dev_id

dev_id is used as a pointer at the end of the call chain, so passing it
as an int makes no sense and can cause crashes if the pointer and int
types have different sizes. For example, if we have 64-bit pointers on
a board, the higher part of dev_id will be removed due to an type cast.

Signed-off-by: Mykyta Poturai <mykyta_poturai@epam.com>
Signed-off-by: Mykola Kvach <mykola_kvach@epam.com>