CHROMIUM: media: virtio: remove current_frame field from stream struct

Field current_frame was used to store currently used stream format
information provided by hypervisor. It was originaly set by
virtio_video_try_fmt function. This function is used to check if
provided format can be handled by the device. Same functionality is
expected from currently unsupported VIDIOC_TRY_FMT. This function modified
state of the driver, which is forbiden by spec for this ioctl.
The field was used only in VIDIOC_S_PARM implementation for encoder.

This patch removes current_frame field, by introducing new function
(virtio_video_find_format). These changes are needed for future support
for VIDIOC_TRY_FMT and to fix VIDIOC_S_PARM. Both are causing
v4l2-compliance to fail. With this patch VIDIOC_S_PARM will no
longer fail in early stages of encoder (before VIDIOC_S_FMT call).

Signed-off-by: Bartłomiej Grzesik <bag@semihalf.com>

BUG=b:160440787
TEST=v4l2-compliance -d /dev/video0
TEST=v4l2-compliance -d /dev/video1
TEST=tast run eve arc.Video*

Change-Id: I9fc3ef0f320125be027a824092fc6d594d698473
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/third_party/kernel/+/3423528


Commit-Queue: Bartłomiej Grzesik <bgrzesik@google.com>
Tested-by: Patryk Busse <pbu@semihalf.com>
Reviewed-by: Alexandre Courbot <acourbot@chromium.org>
Reviewed-by: Patryk Busse <pbu@semihalf.com>
Tested-by: Bartłomiej Grzesik <bag@semihalf.com>