x86, perf_counter, bts: Correct pointer-to-u64 casts

On 32bit, pointers in the DS AREA configuration are cast to
u64. The current (long) cast to avoid compiler warnings results
in a signed 64bit address.

Signed-off-by: Markus Metzger <markus.t.metzger@intel.com>
Acked-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
LKML-Reference: <20090902140615.305889000@intel.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>