env: Replace all open-coded gd->env_valid values with ENV_ flags

Some of these were missed in the conversion.
Signed-off-by: Simon Glass <sjg@chromium.org>
diff --git a/env/flash.c b/env/flash.c
index b60be57..bac10ff 100644
--- a/env/flash.c
+++ b/env/flash.c
@@ -94,7 +94,7 @@
 		gd->env_valid	= ENV_VALID;
 	} else if (!crc1_ok && !crc2_ok) {
 		gd->env_addr	= addr_default;
-		gd->env_valid	= 0;
+		gd->env_valid	= ENV_INVALID;
 	} else if (flag1 == ACTIVE_FLAG && flag2 == OBSOLETE_FLAG) {
 		gd->env_addr	= addr1;
 		gd->env_valid	= ENV_VALID;
@@ -231,7 +231,7 @@
 	}
 
 	gd->env_addr	= (ulong)&default_environment[0];
-	gd->env_valid	= 0;
+	gd->env_valid	= ENV_INVALID;
 	return 0;
 }
 #endif