net: phy: realtek: fix RTL8211F wake-on-lan support

Implement Wake-on-Lan for RTL8211F correctly. The existing
implementation has multiple issues:

1. It assumes that Wake-on-Lan can always be used, whether or not the
   interrupt is wired, and whether or not the interrupt is capable of
   waking the system. This breaks the ability for MAC drivers to detect
   whether the PHY WoL is functional.
2. switching the interrupt pin in the .set_wol() method to PMEB mode
   immediately silences link-state interrupts, which breaks phylib
   when interrupts are being used rather than polling mode.
3. the code claiming to "reset WOL status" was doing nothing of the
   sort. Bit 15 in page 0xd8a register 17 controls WoL reset, and
   needs to be pulsed low to reset the WoL state. This bit was always
   written as '1', resulting in no reset.
4. not resetting WoL state results in the PMEB pin remaining asserted,
   which in turn leads to an interrupt storm. Only resetting the WoL
   state in .set_wol() is not sufficient.
5. PMEB mode does not allow software detection of the wake-up event as
   there is no status bit to indicate we received the WoL packet.
6. across reboots of at least the Jetson Xavier NX system, the WoL
   configuration is preserved.

Fix all of these issues by essentially rewriting the support. We:
1. clear the WoL event enable register at probe time.
2. detect whether we can support wake-up by having a valid interrupt,
   and the "wakeup-source" property in DT. If we can, then we mark
   the MDIO device as wakeup capable, and associate the interrupt
   with the wakeup source.
3. arrange for the get_wol() and set_wol() implementations to handle
   the case where the MDIO device has not been marked as wakeup
   capable (thereby returning no WoL support, and refusing to enable
   WoL support.)
4. avoid switching to PMEB mode, instead using INTB mode with the
   interrupt enable, reconfiguring the interrupt enables at suspend
   time, and restoring their original state at resume time (we track
   the state of the interrupt enable register in .config_intr()
   register.)
5. move WoL reset from .set_wol() to the suspend function to ensure
   that WoL state is cleared prior to suspend. This is necessary
   after the PME interrupt has been enabled as a second WoL packet
   will not re-raise a previously cleared PME interrupt.
6. when a PME interrupt (for wakeup) is asserted, pass this to the
   PM wakeup so it knows which device woke the system.

This fixes WoL support in the Realtek RTL8211F driver when used on the
nVidia Jetson Xavier NX platform, and needs to be applied before stmmac
patches which allow these platforms to forward the ethtool WoL commands
to the Realtek PHY.

Signed-off-by: Russell King (Oracle) <rmk+kernel@armlinux.org.uk>
Reviewed-by: Andrew Lunn <andrew@lunn.ch>
Link: https://patch.msgid.link/E1um8Ld-008jxD-Mc@rmk-PC.armlinux.org.uk
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

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