staging: comedi: icp_multi: remove useless interrupt disable code

This driver does not use interrupts and all the interrupt source are
disabled by icp_multi_reset() when the board is first attached.

Remove the unnecessary, and useless, disable and clearing of interrupts
in the analog input and output (*insn_read) and (*insn_write) functions.

This also removes the need for the private data members 'IntEnable' and
'IntStatus'.

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>