ARM: omap1: add missing include

The omap_serial_wakeup_init() declaration is not visible where it is
defined, so make sure "common.h" is included here, avoiding:

arch/arm/mach-omap1/serial.c:221:12: error: no previous prototype for 'omap_serial_wakeup_init' [-Werror=missing-prototypes]
Acked-by: Tony Lindgren <tony@atomide.com>
Acked-by: Aaro Koskinen <aaro.koskinen@iki.fi>
Link: https://lore.kernel.org/r/20230516153109.514251-8-arnd@kernel.orgSigned-off-by: Arnd Bergmann <arnd@arndb.de>

arch/arm/mach-omap1/serial.c

@@ -19,6 +19,7 @@
 
 #include <asm/mach-types.h>
 
+#include "common.h"
 #include "serial.h"
 #include "mux.h"
 #include "pm.h"