Add dummy functions for Marvell SoC's not equipped with AHCI

Commit r312747 ("Setup decoding windows for ARMADA38X") resulted
in build failing for Marvell platforms, which don't have AHCI controller.
This patch provides a fix by adding dummy functions for such cases.

On the occasion rename register dump routine to decode_win_ahci_dump,
in order to avoid confusion.

Submitted by: Marcin Wojtas <mw@semihalf.com>
Obtained from: Semihalf
Sponsored by: Stormshield