net: phy: introduce genphy_c45_pma_baset1_setup_master_slave()

commit 77f834a1c444f0c2500a072f38b5b17192380be2 from
https://github.com/nxp-auto-linux/linux

Move baset1 specific part of genphy_c45_pma_setup_forced() 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 90532850

)
Signed-off-by: Zhantao Tang <zhantao.tang@windriver.com>