Rather than Unlocking flash during flash object creation, and leaving
the flash possibly continuously unlocked a(s object might bever be freed),
we decide to Unlock then Lock again at each erase or program call.
Users of FlashIAP usually get the minimum programable size
by calling flash.get_page_size(), so let's return the minimum
to allows a most efficient usage of flash.
For F4 devices, this is 1 byte.
For L0 and L1 devices, this is a word (4 bytes).
For L4 devices, this is a double word (8 bytes).
bcostm
Laurent MEUNIER