Rockchip re-uses the ti uart console driver and for aarch32 needs a
specific variant, so add it.
There are also aarch32 ti socs, so it may be useful for them as well
at some point.

Signed-off-by: Heiko Stuebner <heiko@sntech.de>
Change-Id: I31ede7cc7b10347b3691cff051db2b985fd59e17