net: stmmac: add helpers to indicate WoL enable status

Add two helpers to abstract the WoL enable status at the PHY and MAC to
make the code easier to read.

Signed-off-by: Russell King (Oracle) <rmk+kernel@armlinux.org.uk>
Reviewed-by: Andrew Lunn <andrew@lunn.ch>
Link: https://patch.msgid.link/E1umsfP-008vKp-U1@rmk-PC.armlinux.org.uk


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