staging: comedi: s626: tidy the header file a bit

Tidy up the "s626.h" header file a bit, cleaning up the whitespace and
fixing overlength lines.  Add multiple inclusion protection (even though
it's only included once and only by "s626.c").  Remove unnecessary
driver comment near the start of the file as it is more or less the same
as the one in "s626.c".  Remove obviously unused/useless stuff.

I'm not sure what to do about the INTEL/MOTOROLA platform selection in
the file.  I've left it alone (set to INTEL) for now.
Signed-off-by: Ian Abbott <abbotti@mev.co.uk>
Reviewed-by: H Hartley Sweeten <hsweeten@visionengravers.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>