ALSA: Update documents about new bits of xrun_debug proc file

	  bit 2 = Enable additional jiffies check

	  bit 3 = Log hwptr update at each period interrupt

	  bit 4 = Log hwptr update at each snd_pcm_update_hw_ptr()

	  bit 5 = Show last 10 positions on error

	  bit 6 = Do above only once

	When the bit 0 is set, the driver will show the messages to

	kernel log when an xrun is detected.  The debug message is

	Bits 3 and 4 are for logging the hwptr records.  Note that

	these will give flood of kernel messages.

	When bit 5 is set, the driver logs the last 10 xrun errors and

	the proc file shows each jiffies, position, period_size,

	buffer_size, old_hw_ptr, and hw_ptr_base values.

	When bit 6 is set, the full xrun log is shown only once.

card*/pcm*/sub*/info

	The general information of this PCM sub-stream.