perf_event: Fix invalid type in ioctl definition

commit 4c49b128 upstream.

u64 is invalid in userspace headers, including ioctl
definitions; use __u64 instead

Signed-off-by: Arjan van de Ven <arjan@linux.intel.com>
LKML-Reference: <20091113214733.7cd76be9@infradead.org>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>