perf kvm: Use perf_evsel__intval

perf kvm: Use perf_evsel__intval

Using plain raw_field_value(evsel->tp_format) will look at the common
fields as well, and since this tool doesn't need those, speed it up a
bit by looking at just the event specific fields.

Also in general use just evsel and sample, just like was done in 'perf
sched'.

v2: Fixed up test against evsel->name, that contains the subsys name
too, by David Ahern.

Cc: David Ahern <dsahern@gmail.com>
Cc: Dong Hao <haodong@linux.vnet.ibm.com>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Namhyung Kim <namhyung@gmail.com>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Stephane Eranian <eranian@google.com>
Cc: Xiao Guangrong <xiaoguangrong@linux.vnet.ibm.com>
Cc: Runzhen Wang <runzhen@linux.vnet.ibm.com>
Link: http://lkml.kernel.org/n/tip-v9x3q9rv4caxtox7wtjpchq5@git.kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>