Fix misspellings of "system", "controller", "interrupt" and "necessary".

Fix the various misspellings of "system", controller", "interrupt" and
"[un]necessary".

Signed-off-by: Robert P. J. Day <rpjday@mindspring.com>
Signed-off-by: Adrian Bunk <bunk@kernel.org>
diff --git a/sound/soc/soc-core.c b/sound/soc/soc-core.c
index 91651bd..e6a67b5 100644
--- a/sound/soc/soc-core.c
+++ b/sound/soc/soc-core.c
@@ -264,7 +264,7 @@
 }
 
 /*
- * Power down the audio subsytem pmdown_time msecs after close is called.
+ * Power down the audio subsystem pmdown_time msecs after close is called.
  * This is to ensure there are no pops or clicks in between any music tracks
  * due to DAPM power cycling.
  */