ARM: OMAP4: Add minimal support for omap4

This patch adds the support for OMAP4. The platform and machine specific
headers and sources updated for OMAP4430 SDP platform.

OMAP4430 is Texas Instrument's SOC based on ARM Cortex-A9 SMP architecture.
It's a dual core SOC with GIC used for interrupt handling and SCU for cache
coherency.

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