xilinx_timer: Fixed deadlock issue

The timer was deadlocking when the interval was set too low. It would cause a
flood of timer events and the CPU would halt indefinately. This is a known issue
and theres a generic workaround in place in ptimer on ptimer_set_limit(),
however the Xilinx timer uses ptimer_set_count() instead of set_limit. Changed
the call to set_count() to an equivalent call of set_limit() instead, which
brings the workaround into play.
Signed-off-by: NPeter A. G. Crosthwaite <peter.crosthwaite@petalogix.com>
Signed-off-by: NEdgar E. Iglesias <edgar.iglesias@gmail.com>

hw/xilinx_timer.c

@@ -136,7 +136,7 @@ static void timer_enable(struct xlx_timer *xt)
         count = xt->regs[R_TLR];
     else
         count = ~0 - xt->regs[R_TLR];
-    ptimer_set_count(xt->ptimer, count);
+    ptimer_set_limit(xt->ptimer, count, 1);
     ptimer_run(xt->ptimer, 1);
 }