MIPS: bpf: Fix stack space allocation for BPF memwords on MIPS64

When allocating stack space for BPF memwords we need to use the
appropriate 32 or 64-bit instruction to avoid losing the top 32 bits
of the stack pointer.

Signed-off-by: Markos Chandras <markos.chandras@imgtec.com>
Cc: "David S. Miller" <davem@davemloft.net>
Cc: Daniel Borkmann <dborkman@redhat.com>
Cc: Alexei Starovoitov <ast@plumgrid.com>
Cc: netdev@vger.kernel.org
Cc: linux-mips@linux-mips.org
Patchwork: https://patchwork.linux-mips.org/patch/7135/


Signed-off-by: Ralf Baechle <ralf@linux-mips.org>