ARM: OMAP4: suspend: Add MPUSS power domain RETENTION support

This patch adds MPUSS(MPU Sub System) power domain
CSWR(Close Switch Retention) support to system wide suspend.
For MPUSS power domain to hit retention(CSWR or OSWR), both
CPU0 and CPU1 power domains need to be in OFF or DORMANT state,
since CPU power domain CSWR is not supported by hardware

Signed-off-by: Santosh Shilimkar <santosh.shilimkar@ti.com>
Acked-by: Jean Pihet <j-pihet@ti.com>
Reviewed-by: Kevin Hilman <khilman@ti.com>
Tested-by: Vishwanath BS <vishwanath.bs@ti.com>
Signed-off-by: Kevin Hilman <khilman@ti.com>