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/drivers/s390/block/dasd_3990_erp.c b/drivers/s390/block/dasd_3990_erp.c
index 8b9d68f..69402f3 100644
--- a/drivers/s390/block/dasd_3990_erp.c
+++ b/drivers/s390/block/dasd_3990_erp.c
@@ -2001,7 +2001,7 @@
 		switch (sense[28]) {
 		case 0x17:
 			/* issue a Diagnostic Control command with an
-			 * Inhibit Write subcommand and controler modifier */
+			 * Inhibit Write subcommand and controller modifier */
 			erp = dasd_3990_erp_DCTL(erp, 0x20);
 			break;