bpf: disasm: add support for BPF_JMP|BPF_JA|BPF_X

bpf: disasm: add support for BPF_JMP|BPF_JA|BPF_X

Add support for indirect jump instruction.

Example output from bpftool:

   0: (79) r3 = *(u64 *)(r1 +0)
   1: (25) if r3 > 0x4 goto pc+666
   2: (67) r3 <<= 3
   3: (18) r1 = 0xffffbeefspameggs
   5: (0f) r1 += r3
   6: (79) r1 = *(u64 *)(r1 +0)
   7: (0d) gotox r1

Signed-off-by: Anton Protopopov <a.s.protopopov@gmail.com>
Acked-by: Eduard Zingerman <eddyz87@gmail.com>
Link: https://lore.kernel.org/r/20251105090410.1250500-10-a.s.protopopov@gmail.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>