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/ata/pata_sil680.c b/drivers/ata/pata_sil680.c
index 4dc2e73..5c1e9cb 100644
--- a/drivers/ata/pata_sil680.c
+++ b/drivers/ata/pata_sil680.c
@@ -16,7 +16,7 @@
  *
  *	If you have strange problems with nVidia chipset systems please
  *	see the SI support documentation and update your system BIOS
- *	if neccessary
+ *	if necessary
  *
  * TODO
  *	If we know all our devices are LBA28 (or LBA28 sized)  we could use