firmware loader: fix compile warning

The commit ddf1f064("firmware loader: fix build failure
with !CONFIG_FW_LOADER_USER_HELPER") introduces the below
warning:

drivers/base/firmware_class.c:921:13: warning:
'kill_requests_without_uevent' defined but not used [-Wunused-function]

So fix it by defining kill_requests_without_uevent() only if
CONFIG_PM_SLEEP is set.
Reported-by: Stephen Rothwell <sfr@canb.auug.org.au>
Signed-off-by: Ming Lei <ming.lei@canonical.com>
Cc: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/base/firmware_class.c

@@ -917,6 +917,7 @@ static int fw_load_from_user_helper(struct firmware *firmware,
 	return _request_firmware_load(fw_priv, uevent, timeout);
 }
 
+#ifdef CONFIG_PM_SLEEP
 /* kill pending requests without uevent to avoid blocking suspend */
 static void kill_requests_without_uevent(void)
 {
@@ -930,6 +931,7 @@ static void kill_requests_without_uevent(void)
 	}
 	mutex_unlock(&fw_lock);
 }
+#endif
 
 #else /* CONFIG_FW_LOADER_USER_HELPER */
 static inline int
@@ -943,7 +945,9 @@ fw_load_from_user_helper(struct firmware *firmware, const char *name,
 /* No abort during direct loading */
 #define is_fw_load_aborted(buf) false
 
+#ifdef CONFIG_PM_SLEEP
 static inline void kill_requests_without_uevent(void) { }
+#endif
 
 #endif /* CONFIG_FW_LOADER_USER_HELPER */