ARM: OMAP2+: Add minimal 8250 support for GPMC

Just initialize things using the bootloader timings like
we've been doing for the legacy booting too. It should be
possible to patch in the GPMC timings for the based on the
TL16CP743C/TL16C754C manual at:

http://www.ti.com/lit/ds/slls644g/slls644g.pdf



Signed-off-by: Tony Lindgren <tony@atomide.com>