staging: comedi: addi_apci_1032: check INSN_CONFIG_DIGITAL_TRIG shift

staging: comedi: addi_apci_1032: check INSN_CONFIG_DIGITAL_TRIG shift

The `INSN_CONFIG` comedi instruction with sub-instruction code
`INSN_CONFIG_DIGITAL_TRIG` includes a base channel in `data[3]`. This is
used as a right shift amount for other bitmask values without being
checked.  Shift amounts greater than or equal to 32 will result in
undefined behavior.  Add code to deal with this.

Fixes: 33cdce6293dcc ("staging: comedi: addi_apci_1032: conform to new INSN_CONFIG_DIGITAL_TRIG")
Cc: <stable@vger.kernel.org> #3.8+
Signed-off-by: Ian Abbott <abbotti@mev.co.uk>
Link: https://lore.kernel.org/r/20200717145257.112660-3-abbotti@mev.co.uk
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>