net: fec: enable to use PPS feature without time stamping

PPS feature could be useful even when hardware time stamping
of network packets is not in use, so remove offending check
for this condition from fec_ptp_enable_pps().

Signed-off-by: Sergey Organov <sorganov@gmail.com>
Acked-by: Fugang Duan <fugang.duan@nxp.com>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>