MIPS: Use generic atomic64 for 32-bit kernels

MIPS: Use generic atomic64 for 32-bit kernels

The 64-bit kernel has already had its atomic64 functions. Except for that,
we use the generic spinlocked version. The atomic64 types and related
functions are needed for the Linux performance counter subsystem.

Signed-off-by: Deng-Cheng Zhu <dengcheng.zhu@gmail.com>
To: linux-mips@linux-mips.org
Cc: a.p.zijlstra@chello.nl
Cc: paulus@samba.org
Cc: mingo@elte.hu
Cc: acme@redhat.com
Cc: jamie.iles@picochip.com
Patchwork: https://patchwork.linux-mips.org/patch/1361/
Acked-by: David Daney <ddaney@caviumnetworks.com>
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>