x86/bootm: fix error handling in boot_prep_linux(...)

Once we get a zero pointer from load_zimage(...) we must bunch out
instead of continue boot.

Signed-off-by: Hannes Schmelzer <hannes.schmelzer@br-automation.com>
Reviewed-by: Bin Meng <bmeng.cn@gmail.com>

arch/x86/lib/bootm.c

@@ -116,6 +116,10 @@ static int boot_prep_linux(bootm_headers_t *images)
 		char *base_ptr;
 
 		base_ptr = (char *)load_zimage(data, len, &load_address);
+		if (!base_ptr) {
+			puts("## Kernel loading failed ...\n");
+			goto error;
+		}
 		images->os.load = load_address;
 		cmd_line_dest = base_ptr + COMMAND_LINE_OFFSET;
 		images->ep = (ulong)base_ptr;