bpf, arm: Remove unused function emit_a32_alu_r()

Since commit b18bea2a ("ARM: net: bpf: improve 64-bit ALU implementation")
this is unused anymore, so can remove it.

Signed-off-by: YueHaibing <yuehaibing@huawei.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Link: https://lore.kernel.org/bpf/20220611040904.8976-1-yuehaibing@huawei.com