dt-bindings: msm/mdp: Fix up clock related bindings

Address some issues wiht clock related bindings. It's okay to change these
since these bindings aren't used in any dtsi files until now.

MDP5:
- Don't ask for source clock

MDP4:
- Give a better name for MDP_TV_CLK
- Remove TV_SRC
- Add MDP_AXI_CLK

Acked-by: Rob Herring <robh@kernel.org>
Signed-off-by: Archit Taneja <architt@codeaurora.org>
Signed-off-by: Rob Clark <robdclark@gmail.com>