util/amdfwtool: Fix file open error msg

Print out the name of the file that failed to open.

BUG=none
TEST=rerun build-board.sh with missing files
BRANCH=none

Signed-off-by: Eric Peers <epeers@google.com>
Change-Id: Id8543f25ea827fc8764e0315434b834e65bfa7fb
Reviewed-on: https://chromium-review.googlesource.com/2090667
Reviewed-by: Rob Barnes <robbarnes@google.com>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/39598
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Angel Pons <th3fanbus@gmail.com>

util/amdfwtool/amdfwtool.c

@@ -575,7 +575,8 @@ static ssize_t copy_blob(void *dest, const char *src_file, size_t room)
 
 	fd = open(src_file, O_RDONLY);
 	if (fd < 0) {
-		printf("Error: %s\n", strerror(errno));
+		printf("Error opening file: %s: %s\n",
+		       src_file, strerror(errno));
 		return -1;
 	}