UART 8250: Unconditionally provide register constants and use UART8250 prefix.

The register indexes and bitfield masks were guarded by the UART8250 config
options, but it might be (is) necessary to use them in a driver that is
UART8250 like without actually using the 8250 driver itself. To avoid any name
collision with other drivers, also change the constant prefix from UART_ to
UART8250_.

BUG=None
TEST=Built for link, lumpy, pit, and nyan. With this and other changes, got
bootblock serial output on nyan.
BRANCH=None

Change-Id: Ie606d9e0329132961c3004688176204a829569dc
Signed-off-by: Gabe Black <gabeblack@google.com>
Reviewed-on: https://chromium-review.googlesource.com/171336
Reviewed-by: Ronald Minnich <rminnich@chromium.org>
Commit-Queue: Gabe Black <gabeblack@chromium.org>
Tested-by: Gabe Black <gabeblack@chromium.org>
4 files changed