[nvo] Expose nvo_applies()

Signed-off-by: Michael Brown <mcb30@ipxe.org>

src/core/nvo.c

  * @v setting		Setting
  * @ret applies		Setting applies within this settings block
  */
-static int nvo_applies ( struct settings *settings __unused,
-			 struct setting *setting ) {
+int nvo_applies ( struct settings *settings __unused,
+		  struct setting *setting ) {
 
 	return dhcpopt_applies ( setting->tag );
 }

src/include/ipxe/nvo.h

 /** Name of non-volatile options settings block */
 #define NVO_SETTINGS_NAME "nvo"
 
+extern int nvo_applies ( struct settings *settings, struct setting *setting );
 extern void nvo_init ( struct nvo_block *nvo, struct nvs_device *nvs,
 		       size_t address, size_t len,
 		       int ( * resize ) ( struct nvo_block *nvo, size_t len ),