net: fec: Remove duplicated code

`fec_ptp_pps_perout()` reimplements logic already
in `fec_ptp_read()`. Replace with function call.

Signed-off-by: Csókás, Bence <csokas.bence@prolan.hu>
Reviewed-by: Andrew Lunn <andrew@lunn.ch>
Link: https://patch.msgid.link/20240812094713.2883476-2-csokas.bence@prolan.hu


Signed-off-by: Jakub Kicinski <kuba@kernel.org>