powerpc: Switch to using CONFIG_SYS_INIT_SP_OFFSET from CONFIG_SYS_GBL_DATA_OFFSET

In the places where PowerPC references CONFIG_SYS_GBL_DATA_OFFSET it
does so as (CONFIG_SYS_INIT_RAM_ADDR + CONFIG_SYS_GBL_DATA_OFFSET).  And
it defines CONFIG_SYS_GBL_DATA_OFFSET in the same manner that other
architectures define CONFIG_SYS_INIT_SP_OFFSET. Other architectures
define CONFIG_SYS_INIT_SP_ADDR as (CONFIG_SYS_INIT_RAM_ADDR +
CONFIG_SYS_INIT_SP_OFFSET) typically.  Rename things within PowerPC for
consistency with other architectures.

Signed-off-by: Tom Rini <trini@konsulko.com>
diff --git a/include/configs/kmcent2.h b/include/configs/kmcent2.h
index dc45d16..60df6a3 100644
--- a/include/configs/kmcent2.h
+++ b/include/configs/kmcent2.h
@@ -339,9 +339,8 @@
 	  CONFIG_SYS_INIT_RAM_ADDR_PHYS_LOW)
 #define CONFIG_SYS_INIT_RAM_SIZE		0x00004000
 
-#define CONFIG_SYS_GBL_DATA_OFFSET	(CONFIG_SYS_INIT_RAM_SIZE - \
-					GENERATED_GBL_DATA_SIZE)
-#define CONFIG_SYS_INIT_SP_OFFSET	CONFIG_SYS_GBL_DATA_OFFSET
+#define CONFIG_SYS_INIT_SP_OFFSET	(CONFIG_SYS_INIT_RAM_SIZE - GENERATED_GBL_DATA_SIZE)
+#define CONFIG_SYS_INIT_SP_ADDR		(CONFIG_SYS_INIT_RAM_ADDR + CONFIG_SYS_INIT_SP_OFFSET)
 
 #define CONFIG_SYS_MONITOR_LEN		0xc0000         /* 768k */