staging: comedi: ni_6527: reset edge detection registers

`ni6527_reset()` is called to reset various registers when the device is
being initialized or deinitialized.  The edge detection interrupt is
disabled by this function, but the rising and falling edge detection
registers are currently left alone.  Call `ni6527_set_edge_detection()`
to set them to a known, disabled state.

Signed-off-by: Ian Abbott <abbotti@mev.co.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>