ARM: OMAP4+: Add prm and cm base init function.

Instead of statically defining seperate arrays for every OMAP4+ archs,
have a generic init function to populate the arrays. This avoids the
need for creating new array for every arch added in the future that
reuses the prm and cm registers read/write code.

Cc: Paul Walmsley <paul@pwsan.com>
Signed-off-by: R Sricharan <r.sricharan@ti.com>
Signed-off-by: Santosh Shilimkar <santosh.shilimkar@ti.com>
Signed-off-by: Paul Walmsley <paul@pwsan.com>