tools/env: allow equal sign as key value separation

Treat the first equal sign as a key/value separation too. This makes
the script files compatible with mkenvimage input file format. It
won't support variables with equal signs anymore, but this seems not
really like a loss.

Signed-off-by: Stefan Agner <stefan.agner@toradex.com>
diff --git a/tools/env/fw_env.c b/tools/env/fw_env.c
index 6b71acb..0e3e343 100644
--- a/tools/env/fw_env.c
+++ b/tools/env/fw_env.c
@@ -357,7 +357,7 @@
 static char *skip_chars(char *s)
 {
 	for (; *s != '\0'; s++) {
-		if (isblank(*s))
+		if (isblank(*s) || *s == '=')
 			return s;
 	}
 	return NULL;