Staging: line6: fix build error, select SND_RAWMIDI

line6 needs to select SND_RAWMIDI, like many other drivers do.

ERROR: "snd_rawmidi_set_ops" [drivers/staging/line6/line6usb.ko] undefined!
ERROR: "snd_rawmidi_new" [drivers/staging/line6/line6usb.ko] undefined!
ERROR: "snd_rawmidi_transmit_peek" [drivers/staging/line6/line6usb.ko] undefined!
ERROR: "snd_rawmidi_transmit_ack" [drivers/staging/line6/line6usb.ko] undefined!
ERROR: "snd_rawmidi_receive" [drivers/staging/line6/line6usb.ko] undefined!
Signed-off-by: Randy Dunlap <randy.dunlap@oracle.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

drivers/staging/line6/Kconfig

 config LINE6_USB
 	tristate "Line6 USB support"
 	depends on USB && SND
+	select SND_RAWMIDI
 	help
 	  This is a driver for the guitar amp, cab, and effects modeller
 	  PODxt Pro by Line6 (and similar devices), supporting the