perf/x86: Save a few bytes in 'struct x86_pmu'

All these are basically boolean flags, use a bitfield to save a few
bytes.

Suggested-by: Borislav Petkov <bp@amd64.org>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Link: http://lkml.kernel.org/n/tip-vsevd5g8lhcn129n3s7trl7r@git.kernel.org


Signed-off-by: Ingo Molnar <mingo@kernel.org>