x86, perfctr: Remove unused func avail_to_resrv_perfctr_nmi()

avail_to_resrv_perfctr_nmi() is neither EXPORT'd, nor used in
the file. So remove it.

Signed-off-by: Naga Chumbalkar <nagananda.chumbalkar@hp.com>
Acked-by: Cyrill Gorcunov <gorcunov@gmail.com>
Cc: oprofile-list@lists.sf.net
LKML-Reference: <20091224015441.6005.4408.sendpatchset@localhost.localdomain>
Signed-off-by: Ingo Molnar <mingo@elte.hu>