clock-mmss-8994: Remove clock-mmss-mdss driver

Clock framework now has support for orphan clocks, which means clocks
can register even if their parents are not available. Switch to new
implementation and remove clock MMSS MDSS driver. Display related
clocks will be registered together with other MMSS clocks. They will
be available once their parents are registered.

Change-Id: I962175cf7cdfd22058c2024decdefa7430ad643b
Signed-off-by: Junjie Wu <junjiew@codeaurora.org>