serial: sa1100: make sa1100_register_uart_fns a function

Calling sa1100_register_uart_fns() leaves the port structure
unused when CONFIG_SERIAL_SA1100 is disabled, and we get a
compiler warning about that:

arch/arm/mach-sa1100/badge4.c:317:31: warning: 'badge4_port_fns' defined but not used [-Wunused-variable]
 static struct sa1100_port_fns badge4_port_fns __initdata = {

This turns the two empty macros into empty inline functions,
which has the same effect, but lets the compiler know that the
variables are intentionally unused.

Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Acked-by: Linus Walleij <linus.walleij@linaro.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

include/linux/platform_data/sa11x0-serial.h

@@ -26,8 +26,12 @@ struct sa1100_port_fns {
 void sa1100_register_uart_fns(struct sa1100_port_fns *fns);
 void sa1100_register_uart(int idx, int port);
 #else
-#define sa1100_register_uart_fns(fns) do { } while (0)
-#define sa1100_register_uart(idx,port) do { } while (0)
+static inline void sa1100_register_uart_fns(struct sa1100_port_fns *fns)
+{
+}
+static inline void sa1100_register_uart(int idx, int port)
+{
+}
 #endif
 
 #endif