OMAP4: Adding voltage driver support

OMAP4 has three scalable voltage domains vdd_mpu, vdd_iva
and vdd_core. This patch adds the voltage tables and other
configurable voltage processor and voltage controller
settings to control these three scalable domains in OMAP4.

Signed-off-by: Thara Gopinath <thara@ti.com>
Signed-off-by: Kevin Hilman <khilman@deeprootsystems.com>