omap5: Add minimal support for omap5430.

This patch adds the minimal support for OMAP5. The platform and machine
specific headers and sources updated for OMAP5430.

OMAP5430 is Texas Instrument's SOC based on ARM Cortex-A15 SMP architecture.
It's a dual core SOC with GIC used for interrupt handling and SCU for cache
coherency.

Also moved some part of code from the basic platform support that can be made
common for OMAP4/5. Rest is kept out seperately. The same approach is followed
for clocks and emif support in the subsequent patches.

Signed-off-by: sricharan <r.sricharan@ti.com>
Signed-off-by: Sandeep Paulraj <s-paulraj@ti.com>