Staging: line6: needs to select SND_PCM

line6 uses snd_pcm*() functions, so it should select SND_PCM.

ERROR: "snd_pcm_period_elapsed" [drivers/staging/line6/line6usb.ko] undefined!
ERROR: "snd_pcm_set_ops" [drivers/staging/line6/line6usb.ko] undefined!
ERROR: "snd_pcm_lib_free_pages" [drivers/staging/line6/line6usb.ko] undefined!
ERROR: "snd_pcm_lib_ioctl" [drivers/staging/line6/line6usb.ko] undefined!
ERROR: "snd_pcm_lib_malloc_pages" [drivers/staging/line6/line6usb.ko] undefined!
ERROR: "snd_pcm_hw_constraint_ratdens" [drivers/staging/line6/line6usb.ko] undefined!
ERROR: "snd_pcm_format_physical_width" [drivers/staging/line6/line6usb.ko] undefined!
ERROR: "snd_pcm_lib_preallocate_pages_for_all" [drivers/staging/line6/line6usb.ko] undefined!
ERROR: "snd_pcm_new" [drivers/staging/line6/line6usb.ko] undefined!

Signed-off-by: Randy Dunlap <randy.dunlap@oracle.com>
Cc: Markus Grabner <grabner@icg.tugraz.at>
Cc: stable <stable@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>