riscv, bpf: Support unconditional bswap insn

Add support unconditional bswap instruction. Since riscv is always
little-endian, just treat the unconditional scenario the same as
big-endian conversion.

Signed-off-by: Pu Lehui <pulehui@huawei.com>
Acked-by: Björn Töpel <bjorn@kernel.org>
Link: https://lore.kernel.org/r/20230824095001.3408573-7-pulehui@huaweicloud.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>

Author: Pu Lehui

arch/riscv/net/bpf_jit_comp64.c

@@ -1168,6 +1168,7 @@ int bpf_jit_emit_insn(const struct bpf_insn *insn, struct rv_jit_context *ctx,
 		break;
 
 	case BPF_ALU | BPF_END | BPF_FROM_BE:
+	case BPF_ALU64 | BPF_END | BPF_FROM_LE:
 		emit_li(RV_REG_T2, 0, ctx);
 
 		emit_andi(RV_REG_T1, rd, 0xff, ctx);