net: stmmac: remove phylink_config.pcs_poll usage

Phylink will use PCS polling whenever the PCS's poll member is set, so
setting phylink_config.pcs_poll as well is redundant.

Tested-by: Wong Vee Khee &lt;vee.khee.wong@linux.intel.com&gt; # Intel EHL Signed-off-by: Russell King (Oracle) <rmk+kernel@armlinux.org.uk>
Signed-off-by: David S. Miller <davem@davemloft.net>