clk: qcom: Add graphics clock controller driver for SDM845

Add support for the graphics clock controller found on SDM845
based devices. This would allow graphics drivers to probe and
control their clocks.

Signed-off-by: Amit Nischal <anischal@codeaurora.org>
Signed-off-by: Taniya Das <tdas@codeaurora.org>
[sboyd@kernel.org: Collapse return in probe into less lines]
Signed-off-by: Stephen Boyd <sboyd@kernel.org>