[media] [resend] em28xx: Add Plextor ConvertX PX-AV100U to em28xx-cards.c

Adds support for the Plextor ConvertX PX-AV100U, which uses the
eMPIA EM2820 chip.  The device has a device_id of '0x093b, 0xa003'.  I
am using the existing EM2820_BOARD_PINNACLE_DVC_90 board profile, as
the Pinnacle Dazzle DVC 90/100/101/107, Kaiser Baas Video to DVD
maker, and Kworld DVD Maker 2 were already mapped to it.  Some more
background on the device and my testing can be found at
http://www.donkramer.net/plextor_122710.pdf

Signed-off-by: Don Kramer <dgkramer@comcast.net>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>