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>

include/env.h

@@ -71,6 +71,18 @@ int env_get_f(const char *name, char *buf, unsigned int len);
  */
 int env_get_yesno(const char *var);
 
+/**
+ * env_set() - set an environment variable
+ *
+ * This sets or deletes the value of an environment variable. For setting the
+ * value the variable is created if it does not already exist.
+ *
+ * @varname: Variable to adjust
+ * @value: Value to set for the variable, or NULL or "" to delete the variable
+ * @return 0 if OK, 1 on error
+ */
+int env_set(const char *varname, const char *value);
+
 /**
  * env_get_ulong() - Return an environment variable as an integer value
  *