bootstd: Scan all bootdevs in a boot_targets entry

When the boot_targets environment variable is used with the distro-boot
scripts, each device is included individually. For example, if there
are three mmc devices, then we will have something like:

   boot_targets="mmc0 mmc1 mmc2"

In contrast, standard boot supports specifying just the uclass, i.e.:

   boot_targets="mmc"

The intention is that this should scan all MMC devices, but in fact it
currently only scans the first.

Update the logic to handle this case, without required BOOTSTD_FULL to
be enabled.

I believe at least three people reported this, but I found two.

Signed-off-by: Simon Glass <sjg@chromium.org>
Reported-by: Date Huang <tjjh89017@hotmail.com>
Reported-by: Vincent Stehlé <vincent.stehle@arm.com>
diff --git a/boot/bootdev-uclass.c b/boot/bootdev-uclass.c
index 974ddee..44ae98a 100644
--- a/boot/bootdev-uclass.c
+++ b/boot/bootdev-uclass.c
@@ -469,10 +469,11 @@
 			 * if no sequence number was provided, we must scan all
 			 * bootdevs for this media uclass
 			 */
-			if (IS_ENABLED(CONFIG_BOOTSTD_FULL) && seq == -1)
+			if (seq == -1)
 				method_flags |= BOOTFLOW_METHF_SINGLE_UCLASS;
 			if (method_flagsp)
 				*method_flagsp = method_flags;
+			log_debug("method flags %x\n", method_flags);
 			return 0;
 		}
 		log_debug("- no device in %s\n", media->name);
diff --git a/boot/bootflow.c b/boot/bootflow.c
index 6ef62e1..e03932e 100644
--- a/boot/bootflow.c
+++ b/boot/bootflow.c
@@ -260,8 +260,25 @@
 		} else {
 			log_debug("labels %p\n", iter->labels);
 			if (iter->labels) {
-				ret = bootdev_next_label(iter, &dev,
-							 &method_flags);
+				/*
+				 * when the label is "mmc" we want to scan all
+				 * mmc bootdevs, not just the first. See
+				 * bootdev_find_by_label() where this flag is
+				 * set up
+				 */
+				if (iter->method_flags & BOOTFLOW_METHF_SINGLE_UCLASS) {
+					uclass_next_device(&dev);
+					log_debug("looking for next device %s: %s\n",
+						  iter->dev->name,
+						  dev ? dev->name : "<none>");
+				} else {
+					dev = NULL;
+				}
+				if (!dev) {
+					log_debug("looking at next label\n");
+					ret = bootdev_next_label(iter, &dev,
+								 &method_flags);
+				}
 			} else {
 				ret = bootdev_next_prio(iter, &dev);
 				method_flags = 0;