frontends/va: reset roi number at the beginning of each frame so that ROI enable and disabled mixed case can be supported.
What does this MR do and why?
The current strategy for using ROI feature is to assume
ROI is disabled or enabled to the end of session. However
ROI can be enabled or disabled on frame basis, this change
is to change the strategy so that ROI feature can be
stopped and resumed by the application side in the middle.
Signed-off-by: Ruijing Dong <ruijing.dong@amd.com>