msm: camera-7x30: Free buffers from frame queue at open

Free all pending frames in frame queue before cam_frame
thread opens frame device to avoid duplication of buffer
free

Adapted for camera-7x30. Based on this commit:
https://www.codeaurora.org/gitweb/quic/le/?p=kernel/msm.git;a=commitdiff_plain;h=504cb98b3ff613efff254521b32a6611d33a9c84

Signed-off-by: Suresh Vankadara <svankada@codeaurora.org>
Signed-off-by: Thạch Tùng Anh <thachtunganh@gmail.com>