net: bcmgenet: remove unused platform code

net: bcmgenet: remove unused platform code

This effectively reverts b0ba512e25d7 ("net: bcmgenet: enable driver to
work without a device tree"). There has never been an in-tree user of
struct bcmgenet_platform_data, all devices use OF or ACPI.

Signed-off-by: Heiner Kallweit <hkallweit1@gmail.com>
Reviewed-by: Simon Horman <horms@kernel.org>
Reviewed-by: Florian Fainelli <florian.fainelli@broadcom.com>
Link: https://patch.msgid.link/108b4e64-55d4-4b4e-9a11-3c810c319d66@gmail.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>