ARM: OMAP: DRA7: PRM: Add DRA7XX register definitions

Add the new defines for DRA7xx prm module registers.

Signed-off-by: Ambresh K <ambresh@ti.com>
Signed-off-by: Rajendra Nayak <rnayak@ti.com>
[paul@pwsan.com: added generation notation in the comments]
Signed-off-by: Paul Walmsley <paul@pwsan.com>