staging: comedi: plx9052: tidy up the register defines

The PLX INTCSR register defines are a bit wordy and many of them
are not used anywhere.

For aesthetic reasons, remove all the *_MASK and *_DISABLED defines
and rename the remaining bit defines so they are not as wordy.

Convert all the bit defines to bit shifts.

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>