staging: comedi: adl_pci9118: handle hardware errors in interrupt handler

Hardware errors will now always terminate an async command. For aesthetics,
absorb pci9118_decode_error_status() into the interrupt handler and use
the register map defines to remove the "magic" numbers. Refactor the code
to set the appropriate comedi event bits and handle the event.

Remove the unnecessary 'ai_maskerr' and 'ai_maskharderr' members from the
private data.

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>