ALSA: hda - Add description of bdl_pos_adj option

Added a brief description of the new bdl_pos_adj option to
ALSA-Configuration.txt.

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

Documentation/sound/alsa/ALSA-Configuration.txt

@@ -755,6 +755,9 @@ Prior to version 0.9.0rc4 options had a 'snd_' prefix. This was removed.
     model	- force the model name
     position_fix - Fix DMA pointer (0 = auto, 1 = use LPIB, 2 = POSBUF)
     probe_mask  - Bitmask to probe codecs (default = -1, meaning all slots)
+    bdl_pos_adj	- Specifies the DMA IRQ timing delay in samples.
+		Passing -1 will make the driver to choose the appropriate
+		value based on the controller chip.
 
     [Single (global) options]
     single_cmd  - Use single immediate commands to communicate with