perf kvm: Fix spurious '=' use in man page

As option --host and --guest request no input for it, there should not
be a '=' after them in the man page sources.

And --output expects a filename as the input, so there should be a '='
after it.

This patch removes the needless '=' after --guest and --host, and adds a
'=' after --output in perf-kvm.txt.
Signed-off-by: Dongsheng Yang <yangds.fnst@cn.fujitsu.com>
Cc: David Ahern <dsahern@gmail.com>
Cc: Ingo Molnar <mingo@redhat.com>
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/6124d9eb10a3f1f6b399d1db660110bc7a60fd6b.1386197481.git.yangds.fnst@cn.fujitsu.comSigned-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

tools/perf/Documentation/perf-kvm.txt

@@ -60,14 +60,14 @@ There are a couple of variants of perf kvm:
 OPTIONS
 -------
 -i::
---input=::
+--input=<path>::
         Input file name.
 -o::
---output::
+--output=<path>::
         Output file name.
---host=::
+--host::
         Collect host side performance profile.
---guest=::
+--guest::
         Collect guest side performance profile.
 --guestmount=<path>::
 	Guest os root file system mount directory. Users mounts guest os