make visual workstation subarch compile again

This patch fixes the compile error when the i386 subarch visual workstation is turned on:

In file included from linux-2.6.13-rc5/arch/i386/kernel/timers/timer_pit.c:20:
linux-2.6.13-rc5/include/asm-i386/mach-visws/do_timer.h: In function `do_timer_overflow':
linux-2.6.13-rc5/include/asm-i386/mach-visws/do_timer.h:32: error: `i8259A_lock' undeclared (first use in this function) linux-2.6.13-rc5/include/asm-i386/mach-visws/do_timer.h:32: error: (Each undeclared identifier is reported only once linux-2.6.13-rc5/include/asm-i386/mach-visws/do_timer.h:32: error: for each function it appears in.) make[3]: *** [arch/i386/kernel/timers/timer_pit.o] Error 1
make[2]: *** [arch/i386/kernel/timers] Error 2
make[1]: *** [arch/i386/kernel] Error 2
make: *** [_all] Error 2

diff -Nur linux-2.6.13-rc5/include/asm-i386/mach-visws/do_timer.h linux-2.6.13-rc5/include/asm-i386/mach-visws/do_timer.h
@@ -1,6 +1,7 @@
 /* defines for inline arch setup functions */
 
 #include <asm/fixmap.h>
+#include <asm/i8259.h>
 #include "cobalt.h"
 
 static inline void do_timer_interrupt_hook(struct pt_regs *regs)