net: wangxun: use net_prefetch to simplify logic

Use net_prefetch to remove #ifdef and simplify prefetch logic. This
follows the pattern introduced in a previous commit f468f21b ("net:
Take common prefetch code structure into a function"), which replaced
the same logic in all existing drivers at that time.

Signed-off-by: Joe Damato <jdamato@fastly.com>
Reviewed-by: Wojciech Drewek <wojciech.drewek@intel.com>
Link: https://patch.msgid.link/20240729152651.258713-1-jdamato@fastly.com


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