ARM: OMAP2+: CM: add support for getting phys address for a clkctrl register

Add a new CM API for fetching the physical address of a hwmod clkctrl
register. This is needed to map omap hwmods against clkctrl clocks, the
existing support for clkdm address translation was not sufficient to
handle the mutant cases where the clockdomain offset is completely
off from the clkctrl ones.

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