bpf: Fix JIT of is_mov_percpu_addr instruction.

The codegen for is_mov_percpu_addr instruction works for rax/r8 registers
only. Fix it to generate proper x86 byte code for other registers.

Fixes: 7bdbf744 ("bpf: add special internal-only MOV instruction to resolve per-CPU addrs")
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/bpf/20240417214406.15788-1-alexei.starovoitov@gmail.com