Merge branch 'io_uring-zcrx-selftests-more-cleanups'

David Wei says:

====================
io_uring/zcrx: selftests: more cleanups

Patch 1 use rand_port() instead of hard coding port 9999. Patch 2 parses
JSON from ethtool -g instead of string.
====================

Link: https://patch.msgid.link/20250426195525.1906774-1-dw@davidwei.uk
Signed-off-by: Jakub Kicinski <kuba@kernel.org>