tty/vt: consolemap: check put_user() in con_get_unimap()

Only the return value of copy_to_user() is checked in con_get_unimap().
Do the same for put_user() of the count too.

Signed-off-by: Jiri Slaby <jslaby@suse.cz>
Link: https://lore.kernel.org/r/20220607104946.18710-16-jslaby@suse.cz


Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>