env: Move env_set() to env.h

Move env_set() over to the new header file.

Acked-by: Joe Hershberger <joe.hershberger@ni.com>
Signed-off-by: Simon Glass <sjg@chromium.org>
diff --git a/include/net.h b/include/net.h
index 7684076..0262175 100644
--- a/include/net.h
+++ b/include/net.h
@@ -14,6 +14,7 @@
 
 #include <asm/cache.h>
 #include <asm/byteorder.h>	/* for nton* / ntoh* stuff */
+#include <env.h>
 #include <linux/if_ether.h>
 
 #define DEBUG_LL_STATE 0	/* Link local state machine changes */