clk: qcom: 8916: register DSI root clocks during gcc_mdss_probe

Currently the DSI RCG clocks are registered during gcc_probe
before the parents of these clocks are set during the
gcc_mdss_probe. This causes the clock handoff of the DSI
PLL clocks to not happen properly causing the DSI PLL
to get shutdown during the clock_late_init. The DSI PLL clocks
needed to stay enabled during boot up for continuous splash
screen feature. Hence, register these clocks during
gcc_mdss_probe after the parents of these clocks are set.

Change-Id: I4584f80454266e77fc3e15188ea164282b97458d
Signed-off-by: Padmanabhan Komanduru <pkomandu@codeaurora.org>