LoongArch: BPF: Support load-acquire and store-release instructions

LoongArch: BPF: Support load-acquire and store-release instructions

Use the LoongArch common memory access instructions with the barrier
'dbar' to support the BPF load-acquire and store-release instructions.

With this patch, the following testcases passed on LoongArch if the
macro CAN_USE_LOAD_ACQ_STORE_REL is usable in bpf selftests:

  sudo ./test_progs -t verifier_load_acquire
  sudo ./test_progs -t verifier_store_release
  sudo ./test_progs -t verifier_precision/bpf_load_acquire
  sudo ./test_progs -t verifier_precision/bpf_store_release
  sudo ./test_progs -t compute_live_registers/atomic_load_acq_store_rel

Signed-off-by: Tiezhu Yang <yangtiezhu@loongson.cn>
Signed-off-by: Huacai Chen <chenhuacai@loongson.cn>