An erase sector sits in a given flash bank and some MCUs have two flash
banks. If trying to erase a range of sectors and that range crosses from
one flash bank into the next, the original implementation of
`flash_erase()` would not handle this case and would do the wrong thing.
This commit changes `flash_erase()` to only erase a single sector, which
sidesteps the need to handle flash-bank-crossing. Most callers of this
function only need to erase a single sector anyway.
Signed-off-by: Damien George <damien@micropython.org>
b6ab9e420b