env: make env drivers propagate env_import return value

For multiple env drivers to correctly implement fallback when
one environment fails to load (e.g. crc error), the return value
of env_import has to be propagated by all env driver's load
function.

Without this change, the first driver that succeeds to load an
environment with an invalid CRC return 0 (success) and no other
drivers are checked.

Signed-off-by: Simon Goldschmidt <sgoldschmidt@de.pepperl-fuchs.com>
Acked-by: Maxime Ripard <maxime.ripard@free-electrons.com>
diff --git a/env/nand.c b/env/nand.c
index 3e8df39..904f1c4 100644
--- a/env/nand.c
+++ b/env/nand.c
@@ -378,7 +378,7 @@
 		return -EIO;
 	}
 
-	env_import(buf, 1);
+	return env_import(buf, 1);
 #endif /* ! ENV_IS_EMBEDDED */
 
 	return 0;