msm: mdp: Wait unconditionally in internal vsync waits

Do not wait for timestamp to change for internal waits as the
waitqueue can be woken up from places where the vsync timestamp
doesn't change.

Change-Id: I2c2b46c0cfb5e6b8f8d44f719614c25423ab3f9b
Signed-off-by: Naseer Ahmed <naseer@codeaurora.org>