media: v4l2-tpg: fix the SMPTE-2084 transfer function

The SMPTE-2084 transfer functions maps to the luminance range of
0-10000 cd/m^2. Other transfer functions use the traditional range of
0-100 cd/m^2.

I didn't take this into account so the luminance was off by a factor of
100.

Since qv4l2 made the same mistake in reverse I never noticed this until
I tested with actual SMPTE-2084 video.
Signed-off-by: Hans Verkuil <hans.verkuil@cisco.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@s-opensource.com>