net: stmmac: Drop TBI/RTBI PCS flags

First of all the flags are never set by any of the driver parts. If nobody
have them set then the respective statements will always have the same
result. Thus the statements can be simplified or even dropped with no risk
to break things.

Secondly shall any of the TBI or RTBI flag is set the MDIO-bus
registration will be bypassed. Why? It really seems weird. It's perfectly
fine to have a TBI/RTBI-capable PHY configured over the MDIO bus
interface.

Based on the notes above the TBI/RTBI PCS flags can be freely dropped thus
simplifying the driver code.

Reviewed-by: Andrew Halaney <ahalaney@redhat.com>
Signed-off-by: Serge Semin <fancer.lancer@gmail.com>
Signed-off-by: Russell King (Oracle) <rmk+kernel@armlinux.org.uk>
Reviewed-by: Serge Semin <fancer.lancer@gmail.com>
Link: https://lore.kernel.org/r/E1sCErK-00EOPf-EP@rmk-PC.armlinux.org.uk


Signed-off-by: Jakub Kicinski <kuba@kernel.org>