ARM: OMAP4: MPUSS PM: remove unnecessary shim functions for powerdomain control

The OMAP4 MPU subsystem power management code contains several unnecessary
shim functions for powerdomain control; remove them.

Signed-off-by: Paul Walmsley <paul@pwsan.com>
Cc: Santosh Shilimkar <santosh.shilimkar@ti.com>
Cc: Kevin Hilman <khilman@deeprootsystems.com>
Acked-by: Santosh Shilimkar <santosh.shilimkar@ti.com>