net: openvswitch: Use for_each_cpu() where appropriate

Due to legacy reasons, openswitch code opencodes for_each_cpu() to make
sure that CPU0 is always considered.

Since commit c4b2bf6b ("openvswitch: Optimize operations for OvS
flow_stats."), the corresponding  flow->cpu_used_mask is initialized
such that CPU0 is explicitly set.

So, switch the code to using plain for_each_cpu().

Suggested-by: Ilya Maximets <i.maximets@ovn.org>
Signed-off-by: Yury Norov (NVIDIA) <yury.norov@gmail.com>
Acked-by: Ilya Maximets <i.maximets@ovn.org>
Link: https://patch.msgid.link/20250818172806.189325-1-yury.norov@gmail.com


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