net: phy: introduce genphy_c45_pma_baset1_read_master_slave()

commit 493364c3f62b1498f6fb3b61a3ee639a860564ff from
https://github.com/nxp-auto-linux/linux



Move baset1 specific part of genphy_c45_read_pma() code to
separate function to make it reusable by PHY drivers.

Issue: ALB-10440

Signed-off-by: Oleksij Rempel <o.rempel@pengutronix.de>
Reviewed-by: Andrew Lunn <andrew@lunn.ch>
Signed-off-by: David S. Miller <davem@davemloft.net>
(cherry picked from commit b9a366f3)
Signed-off-by: Zhantao Tang <zhantao.tang@windriver.com>