bsps: Move benchmark timer to bsps

This patch is a part of the BSP source reorganization.

Update #3285.

bsps/no_cpu/no_bsp/btimer/timerisr.c

@@ -0,0 +1,38 @@
+/**
+ *  @file
+ *
+ *  If required this ISR is used to bump a count of interval "overflow"
+ *  interrupts which have occurred since the timer was started.  The
+ *  number of overflows is taken into account in the benchmark_timer_read()
+ *  routine if necessary.
+ *
+ *  To reduce overhead this is best to be the "rawest" hardware interupt
+ *  handler you can write.  This should be the only interrupt which can
+ *  occur during the measured time period.
+ *
+ *  @note This file is USUALLY in assembly and is LEAN AND MEAN.
+ *        Any code in this isr is pure overhead which can perturb
+ *        the accuracy of the Timing Test Suite.
+ */
+
+/*
+ *  COPYRIGHT (c) 1989-1999.
+ *  On-Line Applications Research Corporation (OAR).
+ *
+ *  The license and distribution terms for this file may be
+ *  found in the file LICENSE in this distribution or at
+ *  http://www.rtems.org/license/LICENSE.
+ */
+
+#include <rtems.h>
+#include <rtems/btimer.h>
+
+extern uint32_t         _Timer_interrupts;
+
+void timerisr( void )
+{
+  /*
+   *  _Timer_interrupts += TIMER_BETWEEN_OVERFLOWS  (usually in microseconds)
+   *  return from interrupt
+   */
+}