net: stmmac: move serdes power methods to stmmac_[open|release]()

net: stmmac: move serdes power methods to stmmac_[open|release]()

Move the SerDes power up and down calls for the non-"after linkup"
case out of __stmmac_open() and __stmmac_release() into the
stmmac_open() and stmmac_release() methods, which means the SerDes
will only change power state on administrative changes or suspend/
resume, not while changing the interface MTU.

Signed-off-by: Russell King (Oracle) <rmk+kernel@armlinux.org.uk>
Link: https://patch.msgid.link/E1vnDDt-00000007XxF-3uUK@rmk-PC.armlinux.org.uk
Signed-off-by: Jakub Kicinski <kuba@kernel.org>