clk: qcom: Add MSM8998 Global Clock Control (GCC) driver

Add support for the global clock controller found on MSM8998
based devices. This should allow most non-multimedia device
drivers to probe and control their clocks.

Signed-off-by: Joonwoo Park <joonwoop@codeaurora.org>
Signed-off-by: Imran Khan <kimran@codeaurora.org>
Signed-off-by: Rajendra Nayak <rnayak@codeaurora.org>
[bjorn: Specify regs for alpha_plls, fix white spaces and add binding]
Signed-off-by: Bjorn Andersson <bjorn.andersson@linaro.org>
Signed-off-by: Stephen Boyd <sboyd@kernel.org>