staging: comedi: das800: rename CamelCase vars in das800_ai_do_cmd()

Rename the CamelCase variables in das800_ai_do_cmd().

For aesthetic reasons, initialize the variables when they are
declared.

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