net: stmmac: cleared __FPE_REMOVING bit in stmmac_fpe_start_wq()

An issue found when network interface is down and up again, FPE handshake
fails to trigger. This is due to __FPE_REMOVING bit remains being set in
stmmac_fpe_stop_wq() but not cleared in stmmac_fpe_start_wq(). This
cause FPE workqueue task, stmmac_fpe_lp_task() not able to be executed.

To fix this, add clearing __FPE_REMOVING bit in stmmac_fpe_start_wq().

Fixes: 5a558611

 ("net: stmmac: support FPE link partner hand-shaking procedure")
Signed-off-by: Mohammad Athari Bin Ismail <mohammad.athari.ismail@intel.com>
Signed-off-by: David S. Miller <davem@davemloft.net>