media: videodev2.h: add V4L2_FMT_FLAG_DYN_RESOLUTION

Add an enum_fmt format flag to specifically tag coded formats where
dynamic resolution switching is supported by the device.

This is useful for some codec drivers that can support dynamic
resolution switching for one or more of their listed coded formats. It
allows userspace to know whether it should extract the video parameters
itself, or if it can rely on the device to send V4L2_EVENT_SOURCE_CHANGE
when such changes are detected.

Signed-off-by: Maxime Jourdan <mjourdan@baylibre.com>
Reviewed-by: Paul Kocialkowski <paul.kocialkowski@bootlin.com>
Reviewed-by: Alexandre Courbot <acourbot@chromium.org>
Acked-by: Tomasz Figa <tfiga@chromium.org>
Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
Signed-off-by: Mauro Carvalho Chehab <mchehab+samsung@kernel.org>