Revert "net: fec: Use a spinlock to guard `fep->ptp_clk_on`"

This reverts commit b353b241, this is
creating multiple issues, just not ready to be merged yet.

Link: https://lore.kernel.org/all/CAHk-=wj1obPoTu1AHj9Bd_BGYjdjDyPP+vT5WMj8eheb3A9WHw@mail.gmail.com/
Link: https://lore.kernel.org/all/20220907143915.5w65kainpykfobte@pengutronix.de/
Fixes: b353b241

 ("net: fec: Use a spinlock to guard `fep->ptp_clk_on`")
Signed-off-by: Francesco Dolcini <francesco.dolcini@toradex.com>
Reviewed-by: Andrew Lunn <andrew@lunn.ch>
Tested-by: Marc Kleine-Budde <mkl@pengutronix.de>
Signed-off-by: Paolo Abeni <pabeni@redhat.com>