All PAC7311 specific functions remain in pac7311.c. All PAC7302 specific
functions are moved to pac7302.c. The USB device table is also divided into
two parts. This makes it possible to remove the sensor specific decisions
from different functions and also remove sensor infromation from the USB
device table.

The common functions are just copied to both subdrivers. These common
functions can be separated later to a common file or helper module.
Signed-off-by: Marton Nemeth <nm127@freemail.hu>
Signed-off-by: Jean-Francois Moine <moinejf@free.fr>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>