This shows what is _actually_ different for f7. A couple of option
bits, and a renaming of bit 7 of the status register, from Program
Sequence Error to Erase Sequence Error.
We keep the separate implementation of wait_for_last_operation, to meet
the "suggestions" of the reference manual to insert a DSB instruction.
Keeping the renamed bit/functions also requires us to keep separate
implementations of the flag clearing functions
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