net: dsa: mv88e6xxx: Make global2 support mandatory

Early generations of the mv88e6xxx did not have the global 2
registers. In order to keep the driver slim, it was decided to make
the code for these registers optional. Over time, more generations of
switches have been added, always supporting global 2 and adding more
and more registers. No effort has been made to keep these additional
registers also optional to slim the driver down when used for older
generations. Optional global 2 now just gives additional development
and maintenance burden for no real gain.

Make global 2 support always compiled in.

Signed-off-by: Andrew Lunn <andrew@lunn.ch>
Reviewed-by: Florian Fainelli <f.fainelli@gmail.com>
Reviewed-by: Vladimir Oltean <olteanv@gmail.com>
Tested-by: Vladimir Oltean <olteanv@gmail.com>
Link: https://lore.kernel.org/r/20210127003210.663173-1-andrew@lunn.ch


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