drivers: fastboot: zImage flashing is not supported for v3, v4

With vendor boot image introduced in version 3 and 4 of boot
image header, boot information is located in both boot image
and vendor boot image.

Flashing zImage is not supported for version 3 and 4 since this
requires updating vendor boot image and/or generating a new image.

Print an error message when the boot image header version is
greater than 2.

Signed-off-by: Safae Ouajih <souajih@baylibre.com>
Reviewed-by: Mattijs Korpershoek <mkorpershoek@baylibre.com>
Tested-by: Mattijs Korpershoek <mkorpershoek@baylibre.com>
diff --git a/drivers/fastboot/fb_mmc.c b/drivers/fastboot/fb_mmc.c
index 29c18cb..9d25c40 100644
--- a/drivers/fastboot/fb_mmc.c
+++ b/drivers/fastboot/fb_mmc.c
@@ -370,6 +370,14 @@
 		return -1;
 	}
 
+	/* Check if boot image header version is 2 or less */
+	if (hdr->header_version > 2) {
+		pr_err("zImage flashing supported only for boot images v2 and less\n");
+		fastboot_fail("zImage flashing supported only for boot images v2 and less",
+			      response);
+		return -EOPNOTSUPP;
+	}
+
 	/* Check if boot image has second stage in it (we don't support it) */
 	if (hdr->second_size > 0) {
 		pr_err("moving second stage is not supported yet\n");