OMAP3|4: OPP: make omapx_opp_init non-static

omap3 and omap4 opp_init should be made non-static to allow
for platform specific opp table tweaking. making these static
conflicts with the definition in pm.h(global) as well.
we include pm.h as well to ensure that there are no such prototype
conflicts with actual implementation in the future.

Signed-off-by: Nishanth Menon <nm@ti.com>
Signed-off-by: Kevin Hilman <khilman@ti.com>