Similar to how we have abstract defines for the stop bits, parity and
flow control common mode namees, provide abstract flag names for the
"standard" flags. This allows us to start using common API code for v1
and v2 uarts
For stm32f3, drop the "compatibility" defines that simply pollute the
namespace, making it confusingly appear as if f3 has both SR and ISR
registers.
Only pulling out the _common_ stuff. This is a single step in a long
process of eliminating all the duplication and "same, but different"
implementations that are stalling adding nice clean easy support for
l0/f7/l4.
This _ignores_ all currently conflict register definitions, even if they
"do the same thing" it just pulls up the common stuff. A subsequent
commit can look at resolving the implementatations to a single version.
