atheros813x: apply fix from OpenBSD

* https://github.com/openbsd/src/commit/10fd7e381796b38e2a5ec6e1ecb7faaf1087fa13
"Force maximum payload size to 128 bytes for AR816X/AR817x as it triggers"
* could help for #16978

Change-Id: I626e364adcabaa9b3d7e4c1078067c1d82c7d4e3
Reviewed-on: https://review.haiku-os.org/c/haiku/+/5340
Tested-by: Commit checker robot <no-reply+buildbot@haiku-os.org>
Reviewed-by: waddlesplash <waddlesplash@gmail.com>

drivers/network: Move ethernet drivers to an "ether" subdirectory.

Now that there is also a "tap" driver in here, and the WiFi drivers
are also in a subdirectory, moving the physical ethernet device drivers
to a subdirectory also makes sense.

(Briefly) discussed on the mailing lists.