ahci: Make ahci_port_base() non-static to enable overwrite

ahci: Make ahci_port_base() non-static to enable overwrite

To allow a board- / platform-specific ahci_port_base() function, this
patch removes "static inline" and adds __weak to this function. This
will be used by the upcoming Armada 7K/8K SATA / AHCI support, which
unfortunately needs a different port base address calculation.

Signed-off-by: Stefan Roese <sr@denx.de>
Cc: Nadav Haklai <nadavh@marvell.com>
Cc: Neta Zur Hershkovits <neta@marvell.com>
Cc: Kostya Porotchkin <kostap@marvell.com>
Cc: Omri Itach <omrii@marvell.com>
Cc: Igal Liberman <igall@marvell.com>
Cc: Haim Boot <hayim@marvell.com>
Cc: Hanna Hawa <hannah@marvell.com>