perf kvm: Use defines of kvm events

Currently perf-kvm uses string literals for kvm event names, but it
works only for x86, because other architectures may have other names for
those events.

To reduce dependence on architecture, we add <asm/kvm_perf.h> file with
defines for:

- kvm_entry and kvm_exit events,
- exit reason field name in kvm_exit event,
- length of exit reasons strings,
- vcpu_id field name in kvm trace events,

and replace literals in perf-kvm.

Reviewed-by: Cornelia Huck <cornelia.huck@de.ibm.com>
Reviewed-by David Ahern <dsahern@gmail.com>
Signed-off-by: Alexander Yarygin <yarygin@linux.vnet.ibm.com>
Acked-by: Christian Borntraeger <borntraeger@de.ibm.com>
Cc: Christian Borntraeger <borntraeger@de.ibm.com>
Cc: Cornelia Huck <cornelia.huck@de.ibm.com>
Cc: David Ahern <dsahern@gmail.com>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Link: http://lkml.kernel.org/r/1404397747-20939-2-git-send-email-yarygin@linux.vnet.ibm.com


Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>