msm_fb: display: Avoid dsi clock warnings during boot

Correctly set up the dsi_clk_rate in
cont_splash_clk_ctrl before enabling them.

Crs-fixed: 389531
Change-Id: Iee13e6d871ca1fdb7f3f45a5e3b36784145abd86
Signed-off-by: Mayank Goyal <goyalm@codeaurora.org>
msm_fb: display: Add compulsory wait after DTV's TG is disabled.

When DTV timing generator is disabled during dtv_off, a wait for
at least a frame period is required. This is done by waiting on
vsync. In some scenarios, vsync interrupt is received such that, no
wait really happens which results in MDP hangs.
Add wait for 20ms after TG is disabled, to ensure wait for at least
a frame period. Also, print timeout error in case wait for vsync
times out.

Change-Id: I960326e495bc8dc108bf6c6f1994ea3071f1c06d
Signed-off-by: Mayank Chopra <makchopra@codeaurora.org>