omap4: Move SOC specific code from board file

This patch moves OMAP4 soc specific code from 4430sdp board file.
The change is necessary so that newer board support can be added
with minimal changes. This will be also problematic for
multi-board, multi-omap builds.

Signed-off-by: Santosh Shilimkar <santosh.shilimkar@ti.com>
Signed-off-by: Tony Lindgren <tony@atomide.com>