powerpc: Fix misspellings in comments.

Signed-off-by: Adam Buchbinder <adam.buchbinder@gmail.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
diff --git a/arch/powerpc/include/asm/xics.h b/arch/powerpc/include/asm/xics.h
index 0e25bdb..5d61bbc 100644
--- a/arch/powerpc/include/asm/xics.h
+++ b/arch/powerpc/include/asm/xics.h
@@ -1,5 +1,5 @@
 /*
- * Common definitions accross all variants of ICP and ICS interrupt
+ * Common definitions across all variants of ICP and ICS interrupt
  * controllers.
  */