net: pcs: xpcs: avoid reading STAT1 more than once

commit  1eac07fc7696f5e51e979bb00db2f4e984e7099a from
https://github.com/nxp-imx/linux-imx lf-6.1.y

Avoid reading the STAT1 registers more than once while getting the PCS
state, as this register contains latching-low bits that are lost after
the first read.

Signed-off-by: Russell King (Oracle) <rmk+kernel@armlinux.org.uk>
Reviewed-by: Andrew Lunn <andrew@lunn.ch>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
(cherry picked from commit 883a98ed

)
Signed-off-by: Vladimir Oltean <vladimir.oltean@nxp.com>
Signed-off-by: Xiaolei Wang <xiaolei.wang@windriver.com>