V4L/DVB (10654): em28xx: VideoMate For You USB TV box requires tvaudio

V4L/DVB (10654): em28xx: VideoMate For You USB TV box requires tvaudio

As reported by Vitaly Wool <vital@embeddedalley.com>:

> about half a year ago I posted the patch that basically enabled Compro
> VideoMate For You USB TV box support.
> The main problem is I couldn't get the sound working.
> So I kind of decomposed the box and found out the audio decoder chip
> used there was Philips TDA9874A. As far as I can see, it's not supported
> within the em28xx suite although it is for other TV tuner drivers.

A tvaudio modprobing confirms that tda9874a chip is accessible via i2c:

tvaudio: TV audio decoder + audio/video mux driver
tvaudio: known chips: tda9840, tda9873h, tda9874h/a, tda9850, tda9855, tea6300, tea6320, tea6420, tda8425, pic16c54 (PV951), ta8874z
tvaudio' 1-0058: chip found @ 0xb0
tvaudio' 1-0058: tvaudio': chip_read2: reg254=0x11
tvaudio' 1-0058: tvaudio': chip_read2: reg255=0x2
tvaudio' 1-0058: tda9874a_checkit(): DIC=0x11, SIC=0x2.
tvaudio' 1-0058: found tda9874a.
tvaudio' 1-0058: tda9874h/a found @ 0xb0 (em28xx #0)
tvaudio' 1-0058: tda9874h/a: chip_write: reg0=0x0
tvaudio' 1-0058: tda9874h/a: chip_write: reg1=0xc0
tvaudio' 1-0058: tda9874h/a: chip_write: reg2=0x2
tvaudio' 1-0058: tda9874h/a: chip_write: reg11=0x80
tvaudio' 1-0058: tda9874h/a: chip_write: reg12=0x0
tvaudio' 1-0058: tda9874h/a: chip_write: reg13=0x0
tvaudio' 1-0058: tda9874h/a: chip_write: reg14=0x1
tvaudio' 1-0058: tda9874h/a: chip_write: reg15=0x0
tvaudio' 1-0058: tda9874h/a: chip_write: reg16=0x14
tvaudio' 1-0058: tda9874h/a: chip_write: reg17=0x50
tvaudio' 1-0058: tda9874h/a: chip_write: reg18=0xf9
tvaudio' 1-0058: tda9874h/a: chip_write: reg19=0x80
tvaudio' 1-0058: tda9874h/a: chip_write: reg20=0x80
tvaudio' 1-0058: tda9874h/a: chip_write: reg24=0x80
tvaudio' 1-0058: tda9874h/a: chip_write: reg255=0x0
tvaudio' 1-0058: tda9874a_setup(): A2, B/G [0x00].
tvaudio' 1-0058: tda9874h/a: thread started]

This patch automatically loads tvaudio when needed (currently, only
with this board).

Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>