bpf: sock recvbuff must be limited by rmem_max in bpf_setsockopt()

[ Upstream commit c9e4576743eeda8d24dedc164d65b78877f9a98c ]

When sock recvbuff is set by bpf_setsockopt(), the value must by
limited by rmem_max. It is the same with sendbuff.

Fixes: 8c4b4c7e ("bpf: Add setsockopt helper function to bpf")
Signed-off-by: Yafang Shao <laoar.shao@gmail.com>
Acked-by: Martin KaFai Lau <kafai@fb.com>
Acked-by: Lawrence Brakmo <brakmo@fb.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Signed-off-by: Sasha Levin <sashal@kernel.org>