ARM: OMAP4: PRM: move omap4xxx_prm_init earlier in init order

OMAP4 has different ordering of PRM and CM init calls in the early init.
Re-oder these accordingly for OMAP4 also. This is needed so that we
can do some optimizations in the following patches for the PRCM init.

Signed-off-by: Tero Kristo <t-kristo@ti.com>