env: Move env_set_ulong() to env.h

Move env_set_ulong() over to the new header file.

Signed-off-by: Simon Glass <sjg@chromium.org>
Acked-by: Joe Hershberger <joe.hershberger@ni.com>
diff --git a/arch/arm/mach-uniphier/mmc-first-dev.c b/arch/arm/mach-uniphier/mmc-first-dev.c
index 2f1c109..149e662 100644
--- a/arch/arm/mach-uniphier/mmc-first-dev.c
+++ b/arch/arm/mach-uniphier/mmc-first-dev.c
@@ -5,6 +5,7 @@
  */
 
 #include <common.h>
+#include <env.h>
 #include <mmc.h>
 #include <linux/errno.h>