staging: comedi: usbduxfast: use preferred kernel types

As suggested by checkpatch.pl:

CHECK: Prefer kernel type 'u8' over 'uint8_t'
CHECK: Prefer kernel type 's8' over 'int8_t'

For consistency, also change the uint16_t and int16_t types to
u16 and s16.

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>