msm: camera: req_mgr: Increase v4l2 queue length

EIS have 6 fences per request and uses 15 frame window. On camera close
it signals ~90 fences at once. This can overflow v4l2 event queue.

Increase v4l2 queue length for sync events to prevent overflow.

CRs-Fixed: 2498880
Change-Id: Ie886318168e326c1525b4f8be5cacc5f70d0c477
Signed-off-by: Trishansh Bhardwaj <tbhardwa@codeaurora.org>