net: ksz884x: optimize netdev_open flow and remove static variable

remove the static next_jiffies variable, and reinitialize next_jiffies
to simplify netdev_open

Signed-off-by: wujunwen <wudaemon@163.com>
Link: https://lore.kernel.org/r/20220315122857.78601-1-wudaemon@163.com


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