This patch, which basically reverts 6d77444a, fixes an occasional
on-boot or on-capture hang on the XO-1 laptop.

It seems like the cafe hardware is flakier than we thought and that in
some cases, the commands get executed but are never reported as completed
(even if we substantially increase the delays before reading registers).

Reintroduce the 1-second CAFE_SMBUS_TIMEOUT to catch and avoid this
strange hardware bug.
Signed-off-by: Daniel Drake <dsd@laptop.org>
Acked-by: Jonathan Corbet <corbet@lwn.net>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>