media: pci: Fill v4l2_fmtdesc with designated initializers

Replace initialization of static const v4l2_fmtdesc instances that
specify every struct member with designated initializers. This allows
not zeroing the reserved fields explicitly, and will avoid a need to
patch these drivers every time a reserved field is repurposed.

Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Reviewed-by: Niklas Söderlund <niklas.soderlund+renesas@ragnatech.se>
Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>