tty/serial/sirf: fix MODULE_DEVICE_TABLE

This fixes building the sirfsorc-uart driver as a loadable module,
which uses an incorrect MODULE_DEVICE_TABLE, by changing the reference to the
correct symbol.

Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Cc: Jiri Slaby <jslaby@suse.cz>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>