USB: asix: Detect internal PHY and enable/use accordingly

Different AX88772 dongles use different PHYs; the chip is capable of using
both a primary and secondary PHY, and supports an internal and external PHY.

It appears that some DUB-E100 devices use the internal PHY, so trying to use
an external one will not work (note that this is different across revisions,
as well; the "A" and "B" revs of the DUB-E100 use different PHYs!).  The data
sheet for the AX88772 chip specifies that the internal PHY id will be 0x10,
so if that's read from the EEPROM, we should use that rather than attempting
to use an external PHY.

Thanks to Mitch Bradley for pointing this out!

Signed-off-by: Andres Salomon <dilinger@debian.org>
Cc: David Hollis <dhollis@davehollis.com>
Cc: Chris Ball <cjb@laptop.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>