net: phy: realtek: allow CLKOUT to be disabled on RTL8211F(D)(I)-VD-CG

net: phy: realtek: allow CLKOUT to be disabled on RTL8211F(D)(I)-VD-CG

Add CLKOUT disable support for RTL8211F(D)(I)-VD-CG. Like with other PHY
variants, this feature might be requested by customers when the clock
output is not used, in order to reduce electromagnetic interference (EMI).

In the common driver, the CLKOUT configuration is done through PHYCR2.
The RTL_8211FVD_PHYID is singled out as not having that register, and
execution in rtl8211f_config_init() returns early after commit
2c67301584f2 ("net: phy: realtek: Avoid PHYCR2 access if PHYCR2 not
present").

But actually CLKOUT is configured through a different register for this
PHY. Instead of pretending this is PHYCR2 (which it is not), just add
some code for modifying this register inside the rtl8211f_disable_clk_out()
function, and move that outside the code portion that runs only if
PHYCR2 exists.

In practice this reorders the PHYCR2 writes to disable PHY-mode EEE and
to disable the CLKOUT for the normal RTL8211F variants, but this should
be perfectly fine.

It was not noted that RTL8211F(D)(I)-VD-CG would need a genphy_soft_reset()
call after disabling the CLKOUT. Despite that, we do it out of caution
and for symmetry with the other RTL8211F models.

Co-developed-by: Clark Wang <xiaoning.wang@nxp.com>
Signed-off-by: Clark Wang <xiaoning.wang@nxp.com>
Signed-off-by: Vladimir Oltean <vladimir.oltean@nxp.com>
Reviewed-by: Andrew Lunn <andrew@lunn.ch>
Link: https://patch.msgid.link/20251117234033.345679-5-vladimir.oltean@nxp.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>