net: fec: fix the PTP periodic output sysfs interface

net: fec: fix the PTP periodic output sysfs interface

When the PPS channel configuration was implemented, the channel
index for the periodic outputs was configured as the hardware
channel number.

The sysfs interface uses a logical channel index, and rejects numbers
greater than `n_per_out` (see period_store() in ptp_sysfs.c).
That property was left at 1, since the driver implements channel
selection, not simultaneous operation of multiple PTP hardware timer
channels.

A second check in fec_ptp_enable() returns -EOPNOTSUPP when the two
channel numbers disagree, making channels 1..3 unusable from sysfs.

Fix by removing this redundant check in the FEC PTP driver.

Fixes: 566c2d83887f ("net: fec: make PPS channel configurable")
Signed-off-by: Buday Csaba <buday.csaba@prolan.hu>
Link: https://patch.msgid.link/8ec2afe88423c2231f9cf8044d212ce57846670e.1774359059.git.buday.csaba@prolan.hu
Signed-off-by: Jakub Kicinski <kuba@kernel.org>