spelling fixes: arch/sh/

Spelling fixes in arch/sh/.

Signed-off-by: Simon Arlott <simon@fire.lp0.eu>
Signed-off-by: Paul Mundt <lethal@linux-sh.org>
diff --git a/arch/sh/drivers/pci/ops-dreamcast.c b/arch/sh/drivers/pci/ops-dreamcast.c
index 381306c..e1284fc 100644
--- a/arch/sh/drivers/pci/ops-dreamcast.c
+++ b/arch/sh/drivers/pci/ops-dreamcast.c
@@ -57,7 +57,7 @@
  *
  * Also, we could very easily support both Type 0 and Type 1 configurations
  * here, but since it doesn't seem that there is any such implementation in
- * existance, we don't bother.
+ * existence, we don't bother.
  *
  * I suppose if someone actually gets around to ripping the chip out of
  * the BBA and hanging some more devices off of it, then this might be