clk: qcom: Properly support display clocks on msm8974

The display clocks all source from dedicated phy PLLs within their
respective multimedia hardware block. Hook up these PLLs to the
display clocks with the appropriate parent mappings, clock flags,
and the appropriate clock ops. This should allow the display
clocks to work once the appropriate phy PLL driver registers their
PLL clocks.

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