net: phy: realtek: read duplex and gbit master from PHYSR register

The PHYSR MMD register is present and defined equally for all RTL82xx
Ethernet PHYs.
Read duplex and Gbit master bits from rtlgen_decode_speed() and rename
it to rtlgen_decode_physr().

Signed-off-by: Daniel Golle <daniel@makrotopia.org>
Link: https://patch.msgid.link/b9a76341da851a18c985bc4774fa295babec79bb.1728565530.git.daniel@makrotopia.org


Signed-off-by: Paolo Abeni <pabeni@redhat.com>