s626: DIO subdevice 2 should have 16 channels.

s626: DIO subdevice 2 should have 16 channels.

Subdevice 2 (which is a DIO subdevice) has the wrong number of channels,
48 defined by the S626_DIO_CHANNELS macro.  That is the total number of
DIO channels to be split over 3 subdevices (subdevices 2, 3, 4 with 16
channels each).  Fix the number of channels for subdevice 2.

Spotted by H Hartley Sweeten in the "staging" sources.

Signed-off-by: Ian Abbott <abbotti@mev.co.uk>