Revert "crypto: algif_skcipher - Do not dereference ctx without socket lock"

This reverts commit c54ddfbb1b691d77c52b76ca6e13ca7082eb3b82, which
was a poorly backported version of commit
6454c2b83f719057069777132b13949e4c6b6350 upstream.  The small part I
was able to backport makes no sense by itself.

Signed-off-by: Ben Hutchings <ben@decadent.org.uk>

diff --cc crypto/algif_skcipher.c
Simple merge