ARM: omap: pass minimal SoC/board data for UART from dt

Pass minimal data needed for console boot, from dt, for
OMAP4 panda/sdp and OMAP3 beagle boards, and get rid of the
static initialization from generic board file.

Signed-off-by: Rajendra Nayak <rnayak@ti.com>
Reviewed-by: Rob Herring <rob.herring@calxeda.com>
Signed-off-by: Tony Lindgren <tony@atomide.com>