Depending on the controller, the ov7670 sensor may be told to work with a
different clock speed or to use the SMBUS protocol.  Remove the wired-in
code and pass that information from the platform layer.  The Cafe driver
now just assumes it's running on an OLPC XO 1; I do not believe it has ever
run anywhere else.

Cc: Daniel Drake <dsd@laptop.org>
Signed-off-by: Jonathan Corbet <corbet@lwn.net>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>