media: atomisp: fix querycap initialization logic

Some recent changes at V4L2 core changed the way querycap is handled.

Due to that, this warning is generated:

	WARNING: CPU: 1 PID: 503 at drivers/media/v4l2-core/v4l2-dev.c:885 __video_register_device+0x93e/0x1120 [videodev]

as introduced by this commit:

	commit 3c135050


	Author: Hans Verkuil <hverkuil-cisco@xs4all.nl>
	Date:   Tue Jul 23 04:21:25 2019 -0400

	    media: v4l2-dev/ioctl: require non-zero device_caps, verify sane querycap results

	    Now that all V4L2 drivers set device_caps in struct video_device, we can add
	    a check for this to ensure all future drivers fill this in.

The fix is simple: we just need to initialize dev_caps before
registering the V4L2 dev.

While here, solve other problems at VIDIOC_QUERYCAP ioctl.

Reported-by: Patrik Gfeller <patrik.gfeller@gmail.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>