V4L/DVB (11089): au8522: finish conversion to v4l2_device/subdev

Per Hans Verkuil <hverkuil@xs4all.nl> instruction, remove the au8522_command
and replace v4l2-i2c-drv-legacy.h with v4l2-i2c-drv.h

Thanks to Hans Verkuil <hverkuil@xs4all.nl> for reviewing the au8522 analog
support.

Signed-off-by: Devin Heitmueller <dheitmueller@linuxtv.org>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>