net: phy: mscc: fix ptr_ret.cocci warnings

drivers/net/phy/mscc/mscc_ptp.c:1496:1-3: WARNING: PTR_ERR_OR_ZERO can be used

 Use PTR_ERR_OR_ZERO rather than if(IS_ERR(...)) + PTR_ERR

Generated by: scripts/coccinelle/api/ptr_ret.cocci

Fixes: 7d272e63 ("net: phy: mscc: timestamping and PHC support")
CC: Antoine Tenart <antoine.tenart@bootlin.com>
Signed-off-by: kernel test robot <lkp@intel.com>
Signed-off-by: David S. Miller <davem@davemloft.net>