GAS: Export gas_build_initial_resp()

This is needed for some GAS error response messages where the ANQP
Advertisement Protocol element is not used.

src/common/gas.c

@@ -72,7 +72,7 @@ gas_build_resp(u8 action, u8 dialog_token, u16 status_code, u8 frag_id,
 }
 
 
-static struct wpabuf *
+struct wpabuf *
 gas_build_initial_resp(u8 dialog_token, u16 status_code, u16 comeback_delay,
 		       size_t size)
 {

src/common/gas.h

@@ -17,6 +17,8 @@
 #define GAS_H
 
 struct wpabuf * gas_build_comeback_req(u8 dialog_token);
+struct wpabuf * gas_build_initial_resp(u8 dialog_token, u16 status_code,
+				       u16 comeback_delay, size_t size);
 struct wpabuf * gas_anqp_build_initial_req(u8 dialog_token, size_t size);
 struct wpabuf * gas_anqp_build_initial_resp(u8 dialog_token, u16 status_code,
 					    u16 comeback_delay, size_t size);