Blackfin arch: spelling fixes

Signed-off-by: Simon Arlott <simon@fire.lp0.eu>
Signed-off-by: Bryan Wu <bryan.wu@analog.com>

diff --git a/arch/blackfin/kernel/irqchip.c b/arch/blackfin/kernel/irqchip.c
index df5bf02..80996a1 100644
--- a/arch/blackfin/kernel/irqchip.c
+++ b/arch/blackfin/kernel/irqchip.c
@@ -91,7 +91,7 @@
 }
 
 /*
- * do_IRQ handles all hardware IRQ's.  Decoded IRQs should not
+ * do_IRQ handles all hardware IRQs.  Decoded IRQs should not
  * come via this function.  Instead, they should provide their
  * own 'handler'
  */