clk: Separate OF clock code from COMMON_CLK

Clock providers may wish to use the device tree
functionality of the clock framework without using
the COMMON_CLOCK framework. Unconditionally compile
drivers/clk/clk.c and #ifdef out the COMMON_CLK
related code.

Change-Id: I0ba03bbd57879ae17bedcb8c436e031834626673
Signed-off-by: Vikram Mulukutla <markivx@codeaurora.org>