OMAP: powerdomain: Move static allocations from powerdomains.h to a .c file

powerdomains.h header today has only static definitions.  Adding any
function declarations into it and including it in multiple source file
is expected to cause issues.  Hence move all the static definitions
from powerdomains.h file into powerdomains_data.c file.

Also, create a new powerdomain section of the mach-omap2/Makefile, and
rearrange the prcm-common part of the Makefile, now that the
powerdomain code is in its own Makefile section.

Signed-off-by: Rajendra Nayak <rnayak@ti.com>
[paul@pwsan.com: rearrange Makefile changes, tweaked commit message]
Signed-off-by: Paul Walmsley <paul@pwsan.com>
Reviewed-by: Kevin Hilman <khilman@deeprootsystems.com>
Tested-by: Kevin Hilman <khilman@deeprootsystems.com>
Tested-by: Santosh Shilimkar <santosh.shilimkar@ti.com>
Tested-by: Rajendra Nayak <rnayak@ti.com>