frv: cmpxchg: implement cmpxchg64()

frv: cmpxchg: implement cmpxchg64()

FRV supports 64-bit cmpxchg, which is provided by the arch code as
__cmpxchg_64 and subsequently used to implement atomic64_cmpxchg.

This patch hooks up the generic cmpxchg64 API using the same function,
which also provides default definitions of the relaxed, acquire and
release variants.  This fixes the build when COMPILE_TEST=y and
IOMMU_IO_PGTABLE_LPAE=y.

Link: http://lkml.kernel.org/r/[email protected]
Signed-off-by: Will Deacon <[email protected]>
Reported-by: kbuild test robot <[email protected]>
Cc: Joerg Roedel <[email protected]>
Cc: Robin Murphy <[email protected]>
Cc: Peter Zijlstra <[email protected]>
Cc: Ingo Molnar <[email protected]>
Cc: David Howells <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>