ARM: OMAP4: PM: Now remove L4 per clockdomain static depedency with MPU

UART driver slave idle issue has been taken care by driver using hwmod
framework.

So we can now ger rid off the L4 per clockdomain static dependency with
MPU which was used to wrok around UART wakeup and console sluggishnesh issue
on OMAP4 SOCs.

Acked-by: Kevin Hilman <khilman@linaro.org>
Signed-off-by: Santosh Shilimkar <santosh.shilimkar@ti.com>