staging: comedi: comedi.h: checkpatch.pl --strict cleanup

Fix the checkpatch.pl --strict issues:

CHECK: Please use a blank line after function/struct/union/enum declarations

For aesthetics, convert the inline functions into simple macros.

Signed-off-by: H Hartley Sweeten <hsweeten@visionengravers.com>
Cc: Ian Abbott <abbotti@mev.co.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>