ARM: OMAP2+: hwmod: use init-time function pointer for _init_clkdm

Rather than use runtime cpu_is* checking inside _init_clkdm, initialize
SoC specific function pointer at init time.

Signed-off-by: Kevin Hilman <khilman@ti.com>
[paul@pwsan.com: convert to use soc_ops function pointers; remove second para
 from commit message since soc_ops function pointers are now set during hwmod
 layer init]
Signed-off-by: Paul Walmsley <paul@pwsan.com>