ARM: OMAP4+: CM: Move function prototypes to common header for re-use

OMAP5 reuses OMAP4 CM IP block which lets us re-use CM1/CM2 functions.
So move the function prototypes from cm1_44xx.h, cm2_44xx.h to
cm_prm44xx_54xx.h header. The suggestion came from Paul Walmsley
as part of the OMAP5 data file review.

This is preparatory  patch to add OMAP5 CM data file.

Cc: Paul Walmsley <paul@pwsan.com>
Acked-by: Rajendra Nayak <rnayak@ti.com>
Signed-off-by: Santosh Shilimkar <santosh.shilimkar@ti.com>
Signed-off-by: Paul Walmsley <paul@pwsan.com>