sim: mn10300: fix LAST_TIMER_REG typo

The compiler pointed out that we're testing LAST_TIMER_REG and
LAST_COUNTER which are the same value ... and that's because we
set LAST_TIMER_REG to the wrong register.  Fix the typo.

sim/mn10300/dv-mn103tim.c

diff --git a/sim/mn10300/dv-mn103tim.c b/sim/mn10300/dv-mn103tim.c
index 95ebc82..b1844a6 100644
--- a/sim/mn10300/dv-mn103tim.c
+++ b/sim/mn10300/dv-mn103tim.c
@@ -86,7 +86,7 @@
   TM6MDB,
   TM6CA,
   TM6CB,
-  LAST_TIMER_REG = TM6BC,
+  LAST_TIMER_REG = TM6CB,
 };