net: phy: realtek: create rtl8211f_config_phy_eee() helper

net: phy: realtek: create rtl8211f_config_phy_eee() helper

To simplify the rtl8211f_config_init() control flow and get rid of
"early" returns for PHYs where the PHYCR2 register is absent, move the
entire logic sub-block that deals with disabling PHY-mode EEE to a
separate function. There, it is much more obvious what the early
"return 0" skips, and it becomes more difficult to accidentally skip
unintended stuff.

Signed-off-by: Vladimir Oltean <vladimir.oltean@nxp.com>
Link: https://patch.msgid.link/20251117234033.345679-7-vladimir.oltean@nxp.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>