This unifies stm32f1, l1, and f4 convenience functions for adc. The code
should be useable for f2 and f37x as well, but that needs hardware for testing,
and there was no existing implementation. This is the reason for the
"adc_common_v1.c" name, as trying to put all the different families into the
common file name has become too cumbersome.
All of the deprecated routines have been dropped, they've been marked
deprecated for a very long time now, and porting them seemed unnecessary.
This has been tested on f1, l1 and f4 discovery boards, and is based on some
existing l1/f1 unification code from
https://github.com/karlp/libopencm3/tree/rme_l1_master
27bc12de61