msm: vidc: Enable rbr pending flag for readonly buffer

Enable rbr pending flag if firmware response buffer
includes readonly flag to avoid the buffer being
removed from the registered buffers list which is
resulting in below error log prints when release
buffer reference is arrived from firmware.

msm_vidc: err: handle_event_change: data_addr 71f60000,
 extradata_addr 71f3c000 not found

CRs-Fixed: 2110642
Change-Id: I839db6e63ce50ec5e9aa3765b12ed74f613e3195
Signed-off-by: Maheshwar Ajja <majja@codeaurora.org>