serial: Add SupraExpress 336i PnP Voice Modem

Add SupraExpress 336i PnP Voice Modem

Tested and working with the following device: (output from lspnp -v)
01:01.00 SUP1381 (unknown)
    state = active
	io 0x2f8-0x2ff
	irq 3

Signed-off-by: Daniel Gagnon <daniel.gagnon@yahoo.com>
Signed-off-by: Alan Cox <alan@redhat.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>