MIPS: SGI-IP27: Remove not used definition TICK_SIZE in ip27-timer.c

After commit f5ff0a28 ("[MIPS] Use generic NTP code for all MIPS
platforms"), TICK_SIZE is not used in ip27-timer.c for many years,
remove it.
Signed-off-by: Tiezhu Yang <yangtiezhu@loongson.cn>
Signed-off-by: Thomas Bogendoerfer <tsbogend@alpha.franken.de>

arch/mips/sgi-ip27/ip27-timer.c

@@ -28,8 +28,6 @@
 
 #include "ip27-common.h"
 
-#define TICK_SIZE (tick_nsec / 1000)
-
 static int rt_next_event(unsigned long delta, struct clock_event_device *evt)
 {
 	unsigned int cpu = smp_processor_id();