Fix harmless unused warnings in scrypt.h.

scrypt.h

@@ -2,9 +2,12 @@
 #define SCRYPT_H
 
 #ifdef USE_SCRYPT
-extern bool scrypt_test(unsigned char *pdata, const unsigned char *ptarget, uint32_t nonce);
+extern bool scrypt_test(unsigned char *pdata, const unsigned char *ptarget,
+			uint32_t nonce);
 #else /* USE_SCRYPT */
-static inline bool scrypt_test(unsigned char *pdata, const unsigned char *ptarget, uint32_t nonce)
+static inline bool scrypt_test(__maybe_unused unsigned char *pdata,
+			       __maybe_unused const unsigned char *ptarget,
+			       __maybe_unused uint32_t nonce)
 {
 	return false;
 }