mpc85xx: Switch to setting the initial stack pointer more clearly

Currently, since we know that in the combination of
CONFIG_SYS_INIT_RAM_ADDR + CONFIG_SYS_GBL_DATA_OFFSET all of the "high"
bits are in CONFIG_SYS_INIT_RAM_ADDR and "low" bits are in
CONFIG_SYS_GBL_DATA_OFFSET we reference this separately in start.S, but
added together everywhere else.  For clarity consistency, reference the
combined value here instead.

Signed-off-by: Tom Rini <trini@konsulko.com>
diff --git a/arch/powerpc/cpu/mpc85xx/start.S b/arch/powerpc/cpu/mpc85xx/start.S
index 7a079ed..48f06f5 100644
--- a/arch/powerpc/cpu/mpc85xx/start.S
+++ b/arch/powerpc/cpu/mpc85xx/start.S
@@ -1160,8 +1160,8 @@
 	bne	1b
 
 #if CONFIG_VAL(SYS_MALLOC_F_LEN)
-	lis	r4,(CONFIG_SYS_INIT_RAM_ADDR)@h
-	ori	r4,r4,(CONFIG_SYS_GBL_DATA_OFFSET)@l
+	lis	r4,(CONFIG_SYS_INIT_RAM_ADDR + CONFIG_SYS_GBL_DATA_OFFSET)@h
+	ori	r4,r4,(CONFIG_SYS_INIT_RAM_ADDR + CONFIG_SYS_GBL_DATA_OFFSET)@l
 
 	addi	r3,r3,16	/* Pre-relocation malloc area */
 	stw	r3,GD_MALLOC_BASE(r4)