net: pse-pd: tps23881: Fix the device ID check

The DEVID register contains two pieces of information: the device ID in
the upper nibble, and the silicon revision number in the lower nibble.
The driver should work fine with any silicon revision, so let's mask
that out in the device ID check.

Fixes: 20e6d190 ("net: pse-pd: Add TI TPS23881 PSE controller driver")
Signed-off-by: Kyle Swenson <kyle.swenson@est.tech>
Reviewed-by: Thomas Petazzoni <thomas.petazzoni@bootlin.com>
Acked-by: Oleksij Rempel <o.rempel@pengutronix.de>
Signed-off-by: David S. Miller <davem@davemloft.net>