clk: qcom: clock-local2: Only update display RCG if config changes

RCG update will briefly gate the output to ensure glitch free
transition, even if the configuration values are not changed. This
behavior is not acceptable for display clocks because display would
flicker when clock is gated.

Only trigger RCG update when configuration actually changes to avoid
display flicker.

Change-Id: I65b623b55a0abebe99a61137dabb3cfc3e37f2d6
Signed-off-by: Junjie Wu <junjiew@codeaurora.org>