bpf: net: Change sk_getsockopt() to take the sockptr_t argument

bpf: net: Change sk_getsockopt() to take the sockptr_t argument

This patch changes sk_getsockopt() to take the sockptr_t argument
such that it can be used by bpf_getsockopt(SOL_SOCKET) in a
latter patch.

security_socket_getpeersec_stream() is not changed.  It stays
with the __user ptr (optval.user and optlen.user) to avoid changes
to other security hooks.  bpf_getsockopt(SOL_SOCKET) also does not
support SO_PEERSEC.

Signed-off-by: Martin KaFai Lau <martin.lau@kernel.org>
Link: https://lore.kernel.org/r/20220902002802.2888419-1-kafai@fb.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>