Revert "Only provide new libpq sslpasskey hook for openssl-enabled builds"

This reverts commit 9e24109f1a.

This caused build errors when building without openssl, and it's
simplest just to revert it.

src/interfaces/libpq/libpq-fe.h

@@ -620,12 +620,10 @@ extern int	pg_valid_server_encoding_id(int encoding);
 /* == in fe-secure-openssl.c === */
 
 /* Support for overriding sslpassword handling with a callback. */
-#ifdef USE_OPENSSL
 typedef int (*PQsslKeyPassHook_type)(char *buf, int size, PGconn *conn);
 extern PQsslKeyPassHook_type PQgetSSLKeyPassHook(void);
 extern void PQsetSSLKeyPassHook(PQsslKeyPassHook_type hook);
 extern int PQdefaultSSLKeyPassHook(char *buf, int size, PGconn *conn);
-#endif
 
 #ifdef __cplusplus
 }