Add onboard sound device to Device Tree

[notro]

Tested on Pi1 and Pi2 regular kernel with and without DT + ARCH_BCM2835.

Tested from userspace:

$ speaker-test -c2 -t wav
$ omxplayer /usr/share/scratch/Media/Sounds/Vocals/Singer2.wav

omxplayer hangs with no sound on ARCH_BCM2835, reason unknown.

I will enable the driver on ARCH_BCM2835 later when I merge bcm2835_defconfig with bcmrpi_config.

[pelwell]

OK by me.

@popcornmix?

[popcornmix]

Not tested yet (I'm doing something on 3.18 tree).
Can you confirm no observable effect on mach-bcm2708/mach-bcm2709?

[notro]

Can you confirm no observable effect on mach-bcm2708/mach-bcm2709?

I have only tested using the above mentioned commands, which worked fine.
But I have only tested that stereo left/right is working as expected, so I don't know how and probably don't have the equipment to test more channels.

[popcornmix]

I guess I'm more concerned about alsa devices having same names as before so they are detected as they used to be and any alsa config continues to work as before.

[notro]

How do I check that?
These commands give the same output with this PR as with the latest 3.18:

$ aplay -l
**** List of PLAYBACK Hardware Devices ****
card 0: ALSA [bcm2835 ALSA], device 0: bcm2835 ALSA [bcm2835 ALSA]
  Subdevices: 8/8
  Subdevice #0: subdevice #0
  Subdevice #1: subdevice #1
  Subdevice #2: subdevice #2
  Subdevice #3: subdevice #3
  Subdevice #4: subdevice #4
  Subdevice #5: subdevice #5
  Subdevice #6: subdevice #6
  Subdevice #7: subdevice #7
card 0: ALSA [bcm2835 ALSA], device 1: bcm2835 ALSA [bcm2835 IEC958/HDMI]
  Subdevices: 1/1
  Subdevice #0: subdevice #0

$ aplay -L
null
    Discard all samples (playback) or generate zero samples (capture)
default:CARD=ALSA
    bcm2835 ALSA, bcm2835 ALSA
    Default Audio Device
sysdefault:CARD=ALSA
    bcm2835 ALSA, bcm2835 ALSA
    Default Audio Device

[popcornmix]

Yes, that's what I was thinking of. If that reports the same then it seems unlikely to break other alsa apps.