media: staging/most: rename VFL_TYPE_GRABBER to _VIDEO

'GRABBER' is a weird name, all other types map to the /dev
device names. Rename to 'VIDEO' to be consistent with the
other types.

Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
Cc: Christian Gromm <christian.gromm@microchip.com>
Reviewed-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>