powerpc, mpc5xxx: fix missing bootflag init

since:
commit: f05ad9ba "Add a way to skip relocation"

tqm5200s board fails to boot. Reason is that
board_init_f has a function parameter bootflag,
which is not setup in
in arch/powerpc/cpu/mpc5xxx/start.S _start

So board_init_f gets a undefined bootflag,
currently the gd pointer address. Unfortunately
this address sets the GD_FLG_SKIP_RELOC bit,
so u-boot code gets not relocated and u-boot
does not boot ...

Init bootflag with 0, and tqm5200 boots fine again.
Signed-off-by: NHeiko Schocher <hs@denx.de>
Reviewed-by: NSimon Glass <sjg@chromium.org>
Reviewed-by: NYork Sun <yorksun@freescale.com>

arch/powerpc/cpu/mpc5xxx/start.S

@@ -91,6 +91,7 @@ _start:
 	li	r5,GD_SIZE	/* parameter 3:	 count			*/
 	bl	memset
 
+	li	r3, 0		/* parameter 1:	 bootflag		*/
 	bl	board_init_f	/* run 1st part of board init code (in Flash)*/
 	/* NOTREACHED - board_init_f() does not return */
 #else
@@ -169,6 +170,7 @@ lowboot_reentry:
 	/* r3: IMMR */
 	bl	cpu_init_f	/* run low-level CPU init code (in Flash)*/
 
+	li	r3, 0		/* parameter 1:	 bootflag		*/
 	bl	board_init_f	/* run 1st part of board init code (in Flash)*/
 
 	/* NOTREACHED - board_init_f() does not return */