cpu: nrf51: remove obsolete hwtimer support

cpu/nrf51/Makefile.include

@@ -1,6 +1,3 @@
 export CPU_ARCH = cortex-m0
 
-# use hwtimer compatibility module
-USEMODULE += hwtimer_compat
-
 include $(RIOTCPU)/Makefile.include.cortexm_common

cpu/nrf51/include/hwtimer_cpu.h

@@ -1,41 +0,0 @@
-/*
- * Copyright (C) 2014 Freie Universität Berlin
- *
- * This file is subject to the terms and conditions of the GNU Lesser General
- * Public License v2.1. See the file LICENSE in the top level directory for more
- * details.
- */
-
-/**
- * @ingroup         cpu_nrf51822
- * @{
- *
- * @file
- * @brief           CPU specific hwtimer configuration options
- *
- * @author          Hauke Petersen <hauke.peterse@fu-berlin.de>
- */
-
-#ifndef __HWTIMER_CPU_H
-#define __HWTIMER_CPU_H
-
-#ifdef __cplusplus
-extern "C" {
-#endif
-
-/**
- * @name Hardware timer configuration
- * @{
- */
-#define HWTIMER_MAXTIMERS   3               /**< the CPU implementation supports 3 HW timers */
-
-#define HWTIMER_SPEED       1000000         /**< the HW timer runs with 1MHz */
-#define HWTIMER_MAXTICKS    (0xFFFFFF)      /**< 24-bit timer -> see PAN note */
-/** @} */
-
-#ifdef __cplusplus
-}
-#endif
-
-#endif /* __HWTIMER_CPU_H */
-/** @} */