Karl Palsson 7b9baabd69 stm32: drop empty usart.c files
On some targets these weren't even being referenced, on others they
were, in all cases they were empty and contributed no value.

They _actually_ served to declare groupings for doxygen, but we can do
that in a different manner, without having to have dummy files around.
2018-07-03 22:23:00 +00:00
..
2017-03-30 21:48:07 +00:00
2017-06-08 23:01:45 +00:00