linux(4): Eliminate bogus comment.

For the caller is no need for access checking here, as the caller must take care
of EFAULT handling. Moreover, this check would be superfluous, since EFAULT is
extremily rare, and we prefer the fast path.

MFC after: 2 weeks

(cherry picked from commit 80b8d6b144c2f22dda252efe0d9fc70a1c8e15b7)