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/atm/firestream.c b/drivers/atm/firestream.c
index 94ebc9d..f8f7139 100644
--- a/drivers/atm/firestream.c
+++ b/drivers/atm/firestream.c
@@ -1596,7 +1596,7 @@
 
 	/* print the bits in the ISR register. */
 	if (fs_debug & FS_DEBUG_IRQ) {
-		/* The FS_DEBUG things are unneccesary here. But this way it is
+		/* The FS_DEBUG things are unnecessary here. But this way it is
 		   clear for grep that these are debug prints. */
 		fs_dprintk (FS_DEBUG_IRQ,  "IRQ status:");
 		for (i=0;i<27;i++)