treewide: fix "usefull" typo

Signed-off-by: Michael Opdenacker <michael.opdenacker@free-electrons.com>
Signed-off-by: Jiri Kosina <jkosina@suse.cz>
diff --git a/sound/soc/codecs/alc5632.c b/sound/soc/codecs/alc5632.c
index f2e62e4..19e9f22 100644
--- a/sound/soc/codecs/alc5632.c
+++ b/sound/soc/codecs/alc5632.c
@@ -614,7 +614,7 @@
 };
 
 /* Note : pll code from original alc5632 driver. Not sure of how good it is */
-/* usefull only for master mode */
+/* useful only for master mode */
 static const struct _pll_div codec_master_pll_div[] = {
 
 	{  2048000,  8192000,	0x0ea0},