tools: mkfwumdata: Add bank count validation for FWU metadata v2

The FWU metadata specification version 2 supports a maximum of 4 banks.
Add validation to enforce this limit and prevent creation of non-compliant
metadata structures when using version 2.

Without this check, users could inadvertently create invalid metadata by
specifying more than 4 banks, leading to potential compatibility issues
with FWU-compliant firmware update implementations.

Signed-off-by: Kory Maincent <kory.maincent@bootlin.com>
Tested-by: Dario Binacchi <dario.binacchi@amarulasolutions.com>
Signed-off-by: Ilias Apalodimas <ilias.apalodimas@linaro.org>

tools/fwumdata_src/mkfwumdata.c

@@ -471,6 +471,12 @@ int main(int argc, char *argv[])
 		return -EINVAL;
 	}
 
+	if (version == 2 && banks > MAX_BANKS_V2) {
+		fprintf(stderr, "Error: Version 2 supports maximum %d banks, %ld requested.\n",
+			MAX_BANKS_V2, banks);
+		return -EINVAL;
+	}
+
 	/* This command takes UUIDs * images and output file. */
 	if (optind + images + 1 != argc) {
 		fprintf(stderr,