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/include/bootcount.h b/include/bootcount.h
index daee843..8fa8cf8 100644
--- a/include/bootcount.h
+++ b/include/bootcount.h
@@ -9,6 +9,7 @@
 #include <common.h>
 #include <asm/io.h>
 #include <asm/byteorder.h>
+#include <env.h>
 
 #ifdef CONFIG_DM_BOOTCOUNT