clk: msm: mdss: Add support for DSI PLL 1 clock registration

Setup DSI 1 PLL clock heirarchy. This is needed for instances
where we need to turn off the second pll in case of current
leak issue.

Change-Id: I694af1fa9591b2345709687c9e7b1d69f15b56a9
Signed-off-by: Siddhartha Agrawal <agrawals@codeaurora.org>