ARM: OMAP2+: clock: add support for clkdm ops to the low level clk ops

Clock driver requires access to certain clockdomain handling ops once
the code is being moved over under clock driver. Example of this is
clk_enable / clk_disable under omap3 DPLL code. The required clkdm
APIs are now exported through the ti_clk_ll_ops struct.

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