serial: of-serial: compile correctly when 8250 driver is compiled as module

If the 8250 driver is compiled as a module then
CONFIG_SERIAL_8250_MODULE is defined and not CONFIG_SERIAL_8250.

This results in all those code sections that require CONFIG_SERIAL_8250
to be defined are not included.

This patch fixes the situation and allows 8250 and of-serial to
be compiled as a module with the same functionality as when
compiled into the kernel.

Signed-off-by: Martin Sperl <kernel@martin.sperl.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/tty/serial/of_serial.c

@@ -21,6 +21,10 @@
 #include <linux/nwpserial.h>
 #include <linux/clk.h>
 
+#ifdef CONFIG_SERIAL_8250_MODULE
+#define CONFIG_SERIAL_8250 CONFIG_SERIAL_8250_MODULE
+#endif
+
 #include "8250/8250.h"
 
 struct of_serial_info {