clk: qcom: Add support for MSM8960's global clock controller (GCC)

Add a driver for the global clock controller found on MSM8960
based platforms. This should allow most non-multimedia device
drivers to probe and control their clocks.

Signed-off-by: Stephen Boyd <sboyd@codeaurora.org>
Signed-off-by: Mike Turquette <mturquette@linaro.org>