All the "f" type flash parts have an EOP flag, even if it's in different
bit positions. Add a header for this common functionality, and move
it's implementation to the existing common file.
Turns out, there's lots of common code for flash. Pull up prefetch
on/off to start with, as there's only a single bit name different.
Pull up the definitions of common API functions too, starting with
flash_set_ws. Even if the implementations are different, things that
meant to be the same, should be defined centrally.
Extension of code for STM32F1 to allow for dual bank series XL.
Small changes to documentation for F2, F4 and L1 to add a parameter reference.
Tested with STM32F103RBT6
(note: tests show that the PG bit must be cleared after programming, otherwise
a subsequent erase attempt fails. This has been added to flash_program_half_word
for F0 and F1 only. A fix for the other families is not included in this PR.)
