staging: et131x: Remove redundant struct adapter members

adapter->speed_duplex was never referenced.
adapter->registry_phy_coma was always set to zero, even in the vendor driver.

Removing all member references and associated dead code.

Signed-off-by: Mark Einon <mark.einon@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>