The test case only uses one specific sector, but the erase size
is obtained for the whole block device instead. This doesn't work
if different regions of the flash don't have a common erase size.
Fix the issue by getting the erase size at the address we use.
The first revision (1.0) of SFDP (ref: JESD216) does not include
fields for software reset support. It's only been added in the
second revision (1.5) (ref: JESD216A).
Some Mbed OS targets such as DISCO_F746NG include flashes with
legacy SFDP, thus we add an option to preset the reset mode.