There have chance to re-enable the eee_ctrl_timer and fire the timer
in napi callback after delete the timer in .stmmac_release(), which
introduces to access eee registers in the timer function after clocks
are disabled then causes system hang. Found this issue when do
suspend/resume and reboot stress test.

It is safe to delete the timer after napi disabled and disable lpi mode.

Fixes: d765955d ("stmmac: add the Energy Efficient Ethernet support")
Signed-off-by: NFugang Duan <fugang.duan@nxp.com>
Signed-off-by: NJoakim Zhang <qiangqing.zhang@nxp.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>