Add Intel HD Audio support to qemu.

This patch adds three devices to qemu:

intel-hda
	Intel HD Audio Controller, the PCI device.  Provides a HDA bus.
	Emulates ICH6 at the moment.  Adding a ICH9 PCIE
	variant shouldn't be hard.

hda-duplex
	HDA Codec.  Attaches to the HDA bus.  Supports 16bit stereo,
	rates 16k -> 96k, playback, recording and volume control
	(with CONFIG_MIXEMU=y).

hda-output
	HDA Codec without recording support.  Subset of the hda-duplex
	codec.  Use this if you don't want your guests access your mic.

Usage: add '-device intel-hda -device hda-duplex' to your command line.

Tested guests:
 * Linux works.
 * Win7 works.
 * DOS (mpxplay) works.
 * WinXP doesn't work.

[ v2 changes ]
 * Fixed endianess, big endian hosts work now.
 * Fixed some emulation bugs.
 * Added immediate command emulation.
 * Added vmstate support.
 * Make it behave like all other sound card drivers:
   - can be configured via '--audio-card-list=hda'
   - can be added to a VM using '-soundhw hda'
 * Code style fixups.
 * Zapped guest-triggerable asserts.
 * Handle partial reads/writes of audio data correctly.

Cc: malc <av1474@comtv.ru>
Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>
Signed-off-by: malc <av1474@comtv.ru>
