More accurately emulate MIPS Count register.

The MIPS Count register is incremented every 2 cycles, not every
cycle (according to sys/mips/include/clock.h).

Also, instead of using muldiv64() to convert from ticks to nanoseconds:
	y = muldiv64(x, get_ticks_per_sec(), TIMER_FREQ)
where y = number of system ticks and x = device ticks we can just do:
	y = x * 10ns (for 100Mhz clock)

hw/mips/cputimer.c

@@ -25,7 +25,9 @@
 #include "qemu/timer.h"
 #include "sysemu/kvm.h"
 
-#define TIMER_FREQ	100 * 1000 * 1000
+#define CLOCK_PERIOD    10 /* 10 ns period for 100 Mhz frequency */
+#define CYCLES_PER_CNT  2
+#define TIMER_PERIOD    (CYCLES_PER_CNT * CLOCK_PERIOD)
 
 /* XXX: do not use a global */
 uint32_t cpu_mips_get_random (CPUMIPSState *env)
@@ -49,9 +51,8 @@ static void cpu_mips_timer_update(CPUMIPSState *env)
     uint32_t wait;
 
     now = qemu_clock_get_ns(QEMU_CLOCK_VIRTUAL);
-    wait = env->CP0_Compare - env->CP0_Count -
-	    (uint32_t)muldiv64(now, TIMER_FREQ, get_ticks_per_sec());
-    next = now + muldiv64(wait, get_ticks_per_sec(), TIMER_FREQ);
+    wait = env->CP0_Compare - env->CP0_Count - (uint32_t)(now / TIMER_PERIOD);
+    next = now + (uint64_t)wait * CLOCK_PERIOD;
     timer_mod(env->timer, next);
 }
 
@@ -79,8 +80,7 @@ uint32_t cpu_mips_get_count (CPUMIPSState *env)
             cpu_mips_timer_expire(env);
         }
 
-        return env->CP0_Count +
-            (uint32_t)muldiv64(now, TIMER_FREQ, get_ticks_per_sec());
+        return env->CP0_Count + (uint32_t)(now / TIMER_PERIOD);
     }
 }
 
@@ -95,9 +95,8 @@ void cpu_mips_store_count (CPUMIPSState *env, uint32_t count)
         env->CP0_Count = count;
     else {
         /* Store new count register */
-        env->CP0_Count =
-            count - (uint32_t)muldiv64(qemu_clock_get_ns(QEMU_CLOCK_VIRTUAL),
-                                       TIMER_FREQ, get_ticks_per_sec());
+        env->CP0_Count = count -
+            (uint32_t)(qemu_clock_get_ns(QEMU_CLOCK_VIRTUAL) / TIMER_PERIOD);
         /* Update timer timer */
         cpu_mips_timer_update(env);
     }
@@ -121,8 +120,8 @@ void cpu_mips_start_count(CPUMIPSState *env)
 void cpu_mips_stop_count(CPUMIPSState *env)
 {
     /* Store the current value */
-    env->CP0_Count += (uint32_t)muldiv64(qemu_clock_get_ns(QEMU_CLOCK_VIRTUAL),
-                                         TIMER_FREQ, get_ticks_per_sec());
+    env->CP0_Count += (uint32_t)(qemu_clock_get_ns(QEMU_CLOCK_VIRTUAL) /
+                                 TIMER_PERIOD);
 }
 
 static void mips_timer_cb (void *opaque)