ARM: OMAP4+: Change the PRCM structure prototype common for all Socs

The current PRCM structure prototype directly matches the hardware
register layout. So there is a need to change this for every new silicon
revision which has register space changes.

Avoiding this by making the prototye generic and populating the register
addresses seperately for all Socs.

Signed-off-by: R Sricharan <r.sricharan@ti.com>
Signed-off-by: Lokesh Vutla <lokeshvutla@ti.com>