pxe: detect image format before calling bootm/bootz

Trying bootm for zImage will print out several error message which
is not necessary for this case. So detect image format firstly, only
try bootm for legacy and FIT format image then try bootz for others.

This patch needs new function genimg_get_kernel_addr().
Signed-off-by: NBryan Wu <pengw@nvidia.com>

common/cmd_pxe.c

 /*
  * Copyright 2010-2011 Calxeda, Inc.
+ * Copyright (c) 2014, NVIDIA CORPORATION.  All rights reserved.
  *
  * SPDX-License-Identifier:	GPL-2.0+
  */
@@ -609,6 +610,8 @@ static int label_boot(cmd_tbl_t *cmdtp, struct pxe_label *label)
 	char *bootargs;
 	int bootm_argc = 3;
 	int len = 0;
+	ulong kernel_addr;
+	void *buf;
 
 	label_print(label);
 
@@ -771,10 +774,14 @@ static int label_boot(cmd_tbl_t *cmdtp, struct pxe_label *label)
 	if (bootm_argv[3])
 		bootm_argc = 4;
 
+	kernel_addr = genimg_get_kernel_addr(bootm_argv[1]);
+	buf = map_sysmem(kernel_addr, 0);
+	/* Try bootm for legacy and FIT format image */
+	if (genimg_get_format(buf) != IMAGE_FORMAT_INVALID)
 		do_bootm(cmdtp, 0, bootm_argc, bootm_argv);
-
 #ifdef CONFIG_CMD_BOOTZ
-	/* Try booting a zImage if do_bootm returns */
+	/* Try booting a zImage */
+	else
 		do_bootz(cmdtp, 0, bootm_argc, bootm_argv);
 #endif
 	return 1;