mpc83xx: Fix the typo in global data struct

Fix the typo in global_data.h
Signed-off-by: NDave Liu <daveliu@freescale.com>
Signed-off-by: NKim Phillips <kim.phillips@freescale.com>

include/asm-ppc/global_data.h

@@ -63,7 +63,7 @@ typedef	struct	global_data {
 #if defined (CONFIG_MPC834X)
 	u32 usbmph_clk;
 #endif /* CONFIG_MPC834X */
-#if defined(CONFIG_MPC815)
+#if defined(CONFIG_MPC8315)
 	u32 tdm_clk;
 #endif
 #if defined(CONFIG_MPC837X)