m32r: Allow use of atomic64

Atomic64 is now a valid type in Linux. Archs that do not have their own
version of atomic64 operators are to use the generic operations.

The m32r architecture needs to define GENERIC_ATOMIC64.

Link: http://lkml.kernel.org/r/20111013085936.GA13046@elte.hu
Link: http://lkml.kernel.org/r/1318516816.12224.12.camel@gandalf.stny.rr.com
Link: http://lkml.kernel.org/r/20111017185440.GB5545@elte.hu



Acked-by: Hirokazu Takata <takata@linux-m32r.org>
Acked-by: David Rientjes <rientjes@google.com>
Reported-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>