common/cmd_bootm.c: Fix GCC 4.6 warning

cmd_bootm.c: In function 'do_bootz':
cmd_bootm.c:1590:9: warning: variable 'iflag' set but not used
[-Wunused-but-set-variable]

Signed-off-by: Anatolij Gustschin <agust@denx.de>
diff --git a/common/cmd_bootm.c b/common/cmd_bootm.c
index 5685232..45e726a 100644
--- a/common/cmd_bootm.c
+++ b/common/cmd_bootm.c
@@ -1587,7 +1587,6 @@
 
 static int do_bootz(cmd_tbl_t *cmdtp, int flag, int argc, char * const argv[])
 {
-	ulong		iflag;
 	bootm_headers_t	images;
 
 	if (bootz_start(cmdtp, flag, argc, argv, &images))
@@ -1598,7 +1597,7 @@
 	 * overwrite all exception vector code, so we cannot easily
 	 * recover from any failures any more...
 	 */
-	iflag = disable_interrupts();
+	disable_interrupts();
 
 #if defined(CONFIG_CMD_USB)
 	/*