OMAP: clockdomain: Arch specific funcs for clkdm_clk_enable/disable

Define the following architecture specific funtions for omap2/3/4
.clkdm_clk_enable
.clkdm_clk_disable

Convert the platform-independent framework to call these functions.
Also rename the api's by removing the omap2_ preamble.
Hence call omap2_clkdm_k_enable as clkdm_clk_enable and
omap2_clkdm_clk_disable as clkdm_clk_disable.a

Remove unused functions (_enable/_disable_hwsup) and unsed
headers from clockdomain.c file.

Signed-off-by: Rajendra Nayak <rnayak@ti.com>
Signed-off-by: Paul Walmsley <paul@pwsan.com>