ttydev: fix pamc_zilog for tty pointer move

Today's linux-next build (sparc64 defconfig) failed like this:

drivers/serial/sunhv.c: In function `receive_chars':
drivers/serial/sunhv.c:188: error: structure has no member named `tty'
drivers/serial/sunsu.c: In function `receive_chars':
drivers/serial/sunsu.c:314: error: structure has no member named `tty'
drivers/serial/sunsab.c: In function `receive_chars':
drivers/serial/sunsab.c:121: error: structure has no member named `tty'

I applied the following patch (which, again, may not be correct).

Signed-off-by: Stephen Rothwell <sfr@canb.auug.org.au>
Signed-off-by: Alan Cox <alan@redhat.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>