bpf: xfrm: drop dead NULL check in bpf_xdp_get_xfrm_state()

bpf: xfrm: drop dead NULL check in bpf_xdp_get_xfrm_state()

As KF_TRUSTED_ARGS is now considered the default for all kfuncs, the
opts parameter in bpf_xdp_get_xfrm_state() can never be NULL. Verifier
will detect this at load time and will not allow passing NULL to this
function. This matches the documentation above the kfunc that says this
parameter (opts) Cannot be NULL.

Acked-by: Eduard Zingerman <eddyz87@gmail.com>
Signed-off-by: Puranjay Mohan <puranjay@kernel.org>
Link: https://lore.kernel.org/r/20260102180038.2708325-5-puranjay@kernel.org
Signed-off-by: Alexei Starovoitov <ast@kernel.org>