F09x and L4 share the same cselr register, as well as some L0s, factorize
definitions in a new shared header and add helpers.
fyi, that register allows to redefine dma channel peripheral mapping - see
device datasheet for mapping tables.
to remove variations, redundancies, add missing, fix errors. All c files
refer only to the dispatch style headers in /include/stm32. Those headers
#include memorymap.h and cm3/common.h. All references to
these are removed from the family specific headers. Ethernet untouched as
it appears incomplete.
Added dummy spi.c for F0/F3. Fix some doxygen anomalies.
