[IrDA]: KingSun/DonShine USB IrDA dongle support.

This dongle does not follow the usb-irda specification, so it needs its
own special driver. In addition, it uses interrupt endpoints instead of
bulk ones as the rest of USB IrDA dongles supported by Linux (just to be
different?) and data reads need to be parsed to extract the valid bytes
before being unwrapped (details in the comment at the start of the
source). No speed commands have been discovered for this dongle, and I
suspect it does not have any at all.

On plugin, this dongle reports vendor and device IDs: 0x07c0:0x4200 .

The Windows driver that is used normally to control this dongle has a
filename of DSIR620.SYS .

Signed-off-by: Alex Villac�s Lasso <a_villacis@palosanto.com>
Signed-off-by: Samuel Ortiz <samuel@sortiz.org>
Signed-off-by: David S. Miller <davem@davemloft.net>