[media] em28xx: remove dead code line from em28xx_audio_setup()

Setting the value of the chip config register to EM28XX_CHIPCFG_AC97 in
case of a read error is a leftover from the past which is no longer
needed.

Signed-off-by: Frank Schäfer <fschaefer.oss@googlemail.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@osg.samsung.com>