powerpc/bpf/64: add support for atomic fetch operations

Adding instructions for ppc64 for

atomic[64]_fetch_add
atomic[64]_fetch_and
atomic[64]_fetch_or
atomic[64]_fetch_xor

Signed-off-by: Hari Bathini <hbathini@linux.ibm.com>
Tested-by: Naveen N. Rao <naveen.n.rao@linux.vnet.ibm.com> (ppc64le)
Reviewed-by: Naveen N. Rao <naveen.n.rao@linux.vnet.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20220610155552.25892-3-hbathini@linux.ibm.com