ARM: OMAP5 / DRA7: PM / wakeupgen: Enables ES2 PM mode by default

Enables MPUSS ES2 power management mode using ES2_PM_MODE in
AMBA_IF_MODE register.

0x0: OMAP5 ES1 behavior, CPU cores would enter and exit OFF mode together.
     Broken! Fortunately, we do not support this anymore.
0x1: OMAP5 ES2, DRA7 behavior, CPU cores are allowed to enter/exit OFF mode
     independently.

This is one time settings thanks to always ON domain.

Signed-off-by: Santosh Shilimkar <santosh.shilimkar@ti.com>
[nm@ti.com: minor conflict resolutions, consolidation for DRA7]
Signed-off-by: Nishanth Menon <nm@ti.com>
Reviewed-by: Kevin Hilman <khilman@linaro.org>
Tested-by: Kevin Hilman <khilman@linaro.org>