Remove 701-phy_extension.patch from 4.14 and 4.19 kernel, as it's
currenlty broken and fixing doesn't make sense as most of it is
deprecated anyway.
Cc: John Crispin <john@phrozen.org>
Ref: https://bugs.openwrt.org/index.php?do=details&task_id=1982
Signed-off-by: Petr Štetiar <ynezz@true.cz>