V4L/DVB: cx18-alsa: codingstyle fixes

Fix codingstyle issues, and make the minimum version for cx18-alsa required
to be 2.6.17, so that we don't need all the #ifdefs related to the changes
to ALSA structures.

This work was sponsored by ONELAN Limited.

Signed-off-by: Devin Heitmueller <dheitmueller@kernellabs.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>