Staging: comedi: dt9812: fix up a lot of coding style issues

Lots of checkpatch.pl warnings and errors resolved in the
comedi dt9812 usb driver.

Cc: Anders Blomdell <anders.blomdell@control.lth.se>
Cc: David Schleef <ds@schleef.org>
Cc: Frank Mori Hess <fmhess@users.sourceforge.net>
Cc: Ian Abbott <abbotti@mev.co.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>