clk: qcom: mdss: Add mdss pll clock driver support

Each display output interface such as eDP, HDMI and
DSI are clocked by different pll clocks to support
various displays at different resolution simultaneously.
The mdss pll driver handles all these display output
interfaces' pll clocks separately. It also handles their
resources through dtsi configuration.

Change-Id: I1de2ae9a0549de901a6c82ea489199a722344dc4
Signed-off-by: Dhaval Patel <pdhaval@codeaurora.org>