clk: qcom: Add display clock controller driver for SC7180

Add support for the display clock controller found on SC7180
based devices. This would allow display drivers to probe and
control their clocks.

Signed-off-by: Taniya Das <tdas@codeaurora.org>
Link: https://lkml.kernel.org/r/1573812245-23827-4-git-send-email-tdas@codeaurora.org
Signed-off-by: Stephen Boyd <sboyd@kernel.org>