net: Remove smc91111 ethernet driver

This driver has not been converted to DM_ETH.  The migration deadline
passed 2 years ago.

Cc: Linus Walleij <linus.walleij@linaro.org>
Cc: David Feng <fenghua@phytium.com.cn>
Cc: Liviu Dudau <liviu.dudau@foss.arm.com>
Cc: Andre Przywara <andre.przywara@arm.com>
Signed-off-by: Tom Rini <trini@konsulko.com>
Acked-by: Ramon Fried <rfried.dev@gmail.com>