bootstd: android: add support of bootimage v2

Android bootmeth only support boot image v3/4.

Add support of Android Boot Image version 2 [1].
Vendor boot image is only supported in version 3 and 4 so don't try to
read it when header version is less than 3.

[1] https://source.android.com/docs/core/architecture/bootloader/boot-image-header#header-v2

Tested-by: Julien Masson <jmasson@baylibre.com>
Reviewed-by: Mattijs Korpershoek <mkorpershoek@baylibre.com>
Signed-off-by: Guillaume La Roque <glaroque@baylibre.com>
Link: https://lore.kernel.org/r/20241126-adnroidv2-v4-1-11636106dc69@baylibre.com
Signed-off-by: Mattijs Korpershoek <mkorpershoek@baylibre.com>
diff --git a/boot/bootmeth_android.c b/boot/bootmeth_android.c
index 19b1f2c..2e7f85e 100644
--- a/boot/bootmeth_android.c
+++ b/boot/bootmeth_android.c
@@ -259,16 +259,12 @@
 		goto free_priv;
 	}
 
-	if (priv->header_version != 4) {
-		log_debug("only boot.img v4 is supported %u\n", priv->header_version);
-		ret = -EINVAL;
-		goto free_priv;
-	}
-
-	ret = scan_vendor_boot_part(bflow->blk, priv);
-	if (ret < 0) {
-		log_debug("scan vendor_boot failed: err=%d\n", ret);
-		goto free_priv;
+	if (priv->header_version >= 3) {
+		ret = scan_vendor_boot_part(bflow->blk, priv);
+		if (ret < 0) {
+			log_debug("scan vendor_boot failed: err=%d\n", ret);
+			goto free_priv;
+		}
 	}
 
 	/*
@@ -476,12 +472,13 @@
 	if (ret < 0)
 		return log_msg_ret("read boot", ret);
 
-	ret = read_slotted_partition(desc, "vendor_boot", priv->slot, vloadaddr);
-	if (ret < 0)
-		return log_msg_ret("read vendor_boot", ret);
-
+	if (priv->header_version >= 3) {
+		ret = read_slotted_partition(desc, "vendor_boot", priv->slot, vloadaddr);
+		if (ret < 0)
+			return log_msg_ret("read vendor_boot", ret);
+		set_avendor_bootimg_addr(vloadaddr);
+	}
 	set_abootimg_addr(loadaddr);
-	set_avendor_bootimg_addr(vloadaddr);
 
 	ret = bootm_boot_start(loadaddr, bflow->cmdline);