perf: Make cmd_to_page() function more compact

Remove branch for is_perf_command.

Signed-off-by: Wenji Huang <wenji.huang@oracle.com>
Cc: fweisbec@gmail.com
Cc: jkacur@redhat.com
Cc: acme@redhat.com
LKML-Reference: <1263373298-13282-1-git-send-email-wenji.huang@oracle.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>