disp: msm: sde: add frame trigger count to detect frame count in TE period

When qsync is enabled, if there is a large start threshold
window, there might be a case where two frame transfers
could happen in single TE period if second frame trigger
start is issued within the window and could cause tearing
on the screen. This change adds a atomic variable to detect
multiple frame count and adds vsync wait in such cases to
fix this issue. This variable will be set whenever
wr_ptr_irq arrives and will be reset during rd_ptr_irq.

Change-Id: Ice77b8a717a18d39d70dc08647e15b761ad1c126
Signed-off-by: Yashwanth <yvulapu@codeaurora.org>