macintosh/via-macii: Access autopoll_devs when inside lock

The interrupt handler should be excluded when accessing the autopoll_devs
variable.

Fixes: d95fd5fc ("m68k: Mac II ADB fixes") # v5.0+
Signed-off-by: Finn Thain <fthain@telegraphics.com.au>
Tested-by: Stan Johnson <userm57@yahoo.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/5952dd8a9bc9de90f1acc4790c51dd42b4c98065.1593318192.git.fthain@telegraphics.com.au