net: stmmac: Move MAC caps init to phylink MAC caps getter

After a set of recent fixes the stmmac_phy_setup() and
stmmac_reinit_queues() methods have turned to having some duplicated code.
Let's get rid from the duplication by moving the MAC-capabilities
initialization to the PHYLINK MAC-capabilities getter. The getter is
called during each network device interface open/close cycle. So the
MAC-capabilities will be initialized in generic device open procedure and
in case of the Tx/Rx queues re-initialization as the original code
semantics implies.

Signed-off-by: Serge Semin <fancer.lancer@gmail.com>
Reviewed-by: Romain Gantois <romain.gantois@bootlin.com>
Signed-off-by: Paolo Abeni <pabeni@redhat.com>