net: stmmac: remove unnecessary priv->eee_enabled tests

Phylink will not call the mac_disable_tx_lpi() and mac_enable_tx_lpi()
methods randomly - the first method to be called will be the enable
method, and then after, the disable method will be called once between
subsequent enable calls. Thus there is a guaranteed ordering.

Therefore, we know the previous state of priv->eee_enabled, and can
remove it from both methods.

Signed-off-by: Russell King (Oracle) <rmk+kernel@armlinux.org.uk>
Link: https://patch.msgid.link/E1tffdX-003ZI5-UV@rmk-PC.armlinux.org.uk


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