staging: comedi: addi_apci_3501: absorb v_APCI3501_Interrupt()

This driver only has one 'interrupt' function. Absorb the
v_APCI3501_Interrupt() function from hwdrv_apci3501.c into
the driver.

Rename v_ADDI_Interrupt() to apci3501_interrupt() so that the
function has namespace associated with the driver.

Signed-off-by: H Hartley Sweeten <hsweeten@visionengravers.com>
Cc: Ian Abbott <abbotti@mev.co.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>