phy: brcm-sata: Add BCM63138 (DSL) PHY init sequence

The BCM63138 SATA PHY requires a special initialization sequence in
order to operate correctly, mostly tuning incorrect default values.
Implement that sequence and match the documented compatible string as an
entry point into that sequence.

Signed-off-by: Florian Fainelli <f.fainelli@gmail.com>
Signed-off-by: Kishon Vijay Abraham I <kishon@ti.com>