Since commit 1cf4f629d9d2 ("cpu/hotplug: Move online calls to
hotplugged cpu") it is ensured that callbacks of CPU_ONLINE and
CPU_DOWN_PREPARE are processed on the hotplugged cpu. Due to this SMP
function calls are no longer required.
Replace smp_call_function_single() with a direct call of
hw_breakpoint_reset(). To keep the calling convention, interrupts are
explicitely disabled around the call.