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/kernel/signal.h b/arch/powerpc/kernel/signal.h
index 51b2741..be305c8 100644
--- a/arch/powerpc/kernel/signal.h
+++ b/arch/powerpc/kernel/signal.h
@@ -1,5 +1,5 @@
 /*
- *    Copyright (c) 2007 Benjamin Herrenschmidt, IBM Coproration
+ *    Copyright (c) 2007 Benjamin Herrenschmidt, IBM Corporation
  *    Extracted from signal_32.c and signal_64.c
  *
  * This file is subject to the terms and conditions of the GNU General