r8169: align number of tx descriptors with vendor driver

Lowest number of tx descriptors used in the vendor drivers is 256 in
r8169. r8101/r8168/r8125 use 1024 what seems to be the hw limit. Stay
on the safe side and go with 256, same as number of rx descriptors.

Signed-off-by: Heiner Kallweit <hkallweit1@gmail.com>
Link: https://lore.kernel.org/r/a52a6de4-f792-5038-ae2f-240d3b7860eb@gmail.com


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