powerpc/8xx: Declare SPRG2 as a SCRATCH register

Since commit 469d62be9263b92f2c3329540cbb1c076111f4f3, SPRG2 is used as a
scratch register just like SPRG0 and SPRG1. So Declare it as such and fix
the comment which is not valid anymore since that commit.

Signed-off-by: Christophe Leroy <christophe.leroy@c-s.fr>
Signed-off-by: Scott Wood <scottwood@freescale.com>
diff --git a/arch/powerpc/include/asm/reg.h b/arch/powerpc/include/asm/reg.h
index bffd89d..1ff8ba9 100644
--- a/arch/powerpc/include/asm/reg.h
+++ b/arch/powerpc/include/asm/reg.h
@@ -950,7 +950,7 @@
  * 32-bit 8xx:
  *	- SPRG0 scratch for exception vectors
  *	- SPRG1 scratch for exception vectors
- *	- SPRG2 apparently unused but initialized
+ *	- SPRG2 scratch for exception vectors
  *
  */
 #ifdef CONFIG_PPC64
@@ -1060,6 +1060,7 @@
 #ifdef CONFIG_8xx
 #define SPRN_SPRG_SCRATCH0	SPRN_SPRG0
 #define SPRN_SPRG_SCRATCH1	SPRN_SPRG1
+#define SPRN_SPRG_SCRATCH2	SPRN_SPRG2
 #endif