porting/nimble/hal_timer: fix NVIC setup

In commit ab53154 platform specific handling of the NVIC setup
for the timers priority and vectors were revertet. This leads
to problems on certain platforms, e.g. interrupt priority
related hard-faults on RIOT. This commit re-introduces the
platform specific setup.

porting/nimble/src/hal_timer.c

@@ -538,8 +538,14 @@ hal_timer_init(int timer_num, void *cfg)
 
     /* Disable IRQ, set priority and set vector in table */
     NVIC_DisableIRQ(irq_num);
+#ifndef RIOT_VERSION
     NVIC_SetPriority(irq_num, (1 << __NVIC_PRIO_BITS) - 1);
+#endif
+#if MYNEWT
     NVIC_SetVector(irq_num, (uint32_t)irq_isr);
+#else
+    ble_npl_hw_set_isr(irq_num, irq_isr);
+#endif
 
     return 0;