ALSA: emu10k1 - delay the PCM interrupts (add pcm_irq_delay parameter)

ALSA: emu10k1 - delay the PCM interrupts (add pcm_irq_delay parameter)

commit 56385a12d9bb9e173751f74b6c430742018cafc0 upstream.

With some hardware combinations, the PCM interrupts are acknowledged
before the period boundary from the emu10k1 chip. The midlevel PCM code
gets confused and the playback stream is interrupted.

It seems that the interrupt processing shift by 2 samples is enough
to fix this issue. This default value does not harm other,
non-affected hardware.

More information: Kernel bugzilla bug#16300

[A copmile warning fixed by tiwai]

Signed-off-by: Jaroslav Kysela <perex@perex.cz>
Signed-off-by: Takashi Iwai <tiwai@suse.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>