Restore the vcs_size() handling in vcs_read() to what
it had been in previous version.

Fixes: 226fae12 ("vc_screen: move load of struct vc_data pointer in vcs_read() to avoid UAF")
Suggested-by: NJiri Slaby <jirislaby@kernel.org>
Signed-off-by: NGeorge Kennedy <george.kennedy@oracle.com>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>