phy: berlin-sata: Move PHY_BASE into private data struct

Currently, Berlin SATA PHY driver assumes PHY_BASE address being
constant. While this PHY_BASE is correct for BG2Q, older BG2 PHY_BASE
is different. Prepare the driver for BG2 support by moving the phy_base
into private driver data.

Acked-by: Antoine Ténart <antoine.tenart@free-electrons.com>
Signed-off-by: Sebastian Hesselbarth <sebastian.hesselbarth@gmail.com>
Signed-off-by: Kishon Vijay Abraham I <kishon@ti.com>