register_wide_hw_breakpoint(): modify to accept step_needed arg

arch like ARM64 expects 'step_needed = 1'  in order to use default
single step handler. Therefore, modify register_wide_hw_breakpoint()
implementation,so that we can set this field in struct hw_perf_event to
be used later by arch specific code.

Other arch will not have any affect as they do not use it so far.

Signed-off-by: Pratyush Anand <panand@redhat.com>