perf top: Add mwait_idle_with_hints to skip_symbols[]

We skip the display of idle routine related symbols because
they are typically rather erratic and confusing: they depend
on the IRQ rate or sometimes they dominate the profile if
they are polling based.

Add mwait_idle_with_hints too, this is one of the idle
routines on x86.

Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>