media/gpu/v4l2: remove unnecessary VIDIOC_QBUF ioctl calls
for CAPTURE buffers with key frames

This CL fixes issues where unnecessary VIDIOC_QBUF ioctl calls are made
for CAPTURE buffers after decoding key frames. First, only 1 CAPTURE
buffer can be queued after the first key frame decoding. Second, CAPTURE
buffer index used for previous frame can be tracked to avoid unnecessary
VIDIOC_QBUF ioctl call with key frames.

Bug: b:216678334
TEST: v4l2_stateless_decoder --video=crowd_run_256X144_fr15_bd8_8buf_l1_20210312.ivf on asurada
Change-Id: Iebdb492878e0be8db50c83040b613db84552ec99
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/3440378
Reviewed-by: Miguel Casas-Sanchez <mcasas@chromium.org>
Commit-Queue: Steve Cho <stevecho@chromium.org>
Cr-Commit-Position: refs/heads/main@{#972813}