ARM: OMAP4: PM: Refine the APIs to support OMAP4 features.

The proper Macros have to be used for platform specific calls and
some of the compiling requirements and init calls are taken care of.

Signed-off-by: Abhijit Pagare <abhijitpagare@ti.com>
Signed-off-by: Paul Walmsley <paul@pwsan.com>
Cc: Benoit Cousson <b-cousson@ti.com>
Cc: Rajendra Nayak <rnayak@ti.com>