mpc85xx: Initial SP alignment is wrong.

PowerPC mandates SP to be 16 bytes aligned.
Furthermore, a stack frame is added, pointing to the reset vector
which may in the way when gdb is walking the stack because
the reset vector may not accessible depending on emulator settings.
Also use a temp register so gdb doesn't pick up intermediate values.

Signed-off-by: Joakim Tjernlund <Joakim.Tjernlund@transmode.se>
Acked-by: Kumar Gala <galak@kernel.crashing.org>
Signed-off-by: Andy Fleming <afleming@freescale.com>

arch/powerpc/cpu/mpc85xx/start.S

@@ -855,18 +855,12 @@ version_string:
 	.globl	_start_cont
 _start_cont:
 	/* Setup the stack in initial RAM,could be L2-as-SRAM or L1 dcache*/
-	lis	r1,CONFIG_SYS_INIT_RAM_ADDR@h
-	ori	r1,r1,CONFIG_SYS_INIT_SP_OFFSET@l
-
+	lis	r3,(CONFIG_SYS_INIT_RAM_ADDR)@h
+	ori	r3,r3,((CONFIG_SYS_INIT_SP_OFFSET-16)&~0xf)@l /* Align to 16 */
 	li	r0,0
-	stwu	r0,-4(r1)
-	stwu	r0,-4(r1)		/* Terminate call chain */
-
-	stwu	r1,-8(r1)		/* Save back chain and move SP */
-	lis	r0,RESET_VECTOR@h	/* Address of reset vector */
-	ori	r0,r0,RESET_VECTOR@l
-	stwu	r1,-8(r1)		/* Save back chain and move SP */
-	stw	r0,+12(r1)		/* Save return addr (underflow vect) */
+	stw	r0,0(r3)	/* Terminate Back Chain */
+	stw	r0,+4(r3)	/* NULL return address. */
+	mr	r1,r3		/* Transfer to SP(r1) */
 
 	GET_GOT
 	bl	cpu_init_early_f