riscv: bpf: Avoid breaking W^X

[ Upstream commit fc850476 ]

We allocate Non-executable pages, then call bpf_jit_binary_lock_ro()
to enable executable permission after mapping them read-only. This is
to prepare for STRICT_MODULE_RWX in following patch.

Signed-off-by: Jisheng Zhang <jszhang@kernel.org>
Signed-off-by: Palmer Dabbelt <palmerdabbelt@google.com>
Stable-dep-of: c56fb2aa ("riscv, bpf: Fix inconsistent JIT image generation")
Signed-off-by: Sasha Levin <sashal@kernel.org>