drivers/tty/serial: delete unused MODULE_DEVICE_TABLE from atmel_serial.c

In commit c39dfebc ("drivers/tty/serial:
make serial/atmel_serial.c explicitly non-modular") we removed the code
relating to modular support since it currently only supports built in.

However, when redoing my build coverage for mips allmodconfig, which
sets CONFIG_OF, I noticed a remaining line that needs to be removed,
else we will get a build failure for an undefined module macro.

Unfortunately this didn't appear for any of the other arch I tested
more frequently, such as ARM.

Since MODULE_DEVICE_TABLE is a no-op for non-modular code, we can just
remove the offending line.

Fixes: c39dfebc ("drivers/tty/serial: make serial/atmel_serial.c explicitly non-modular")
Cc: Nicolas Ferre <nicolas.ferre@atmel.com>
Cc: Jiri Slaby <jslaby@suse.com>
Reported-by: NSudip Mukherjee <sudip@vectorindia.org>
Signed-off-by: NPaul Gortmaker <paul.gortmaker@windriver.com>
Acked-by: NNicolas Ferre <nicolas.ferre@atmel.com>
Acked-by: NSudip Mukherjee <sudip@vectorindia.org>
Signed-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/tty/serial/atmel_serial.c

@@ -188,8 +188,6 @@ static const struct of_device_id atmel_serial_dt_ids[] = {
 	{ .compatible = "atmel,at91sam9260-usart" },
 	{ /* sentinel */ }
 };
-
-MODULE_DEVICE_TABLE(of, atmel_serial_dt_ids);
 #endif
 
 static inline struct atmel_uart_port *