net: stmmac: Set MAC's flow control register to reflect current settings

Currently, pause frame register GMAC_RX_FLOW_CTRL_RFE is not updated
correctly when 'ethtool -A <IFACE> autoneg off rx off tx off' command
is issued. This fix ensures the flow control change is reflected directly
in the GMAC_RX_FLOW_CTRL_RFE register.

Fixes: 46f69ded ("net: stmmac: Use resolved link config in mac_link_up()")
Cc: <stable@vger.kernel.org> # 5.10.x
Signed-off-by: Goh, Wei Sheng <wei.sheng.goh@intel.com>
Signed-off-by: Noor Azura Ahmad Tarmizi <noor.azura.ahmad.tarmizi@intel.com>
Signed-off-by: David S. Miller <davem@davemloft.net>