ata: ahci_brcm: Allow using driver or DSL SoCs

The Broadcom STB AHCI controller is the same as the one found on DSL
SoCs, so we will utilize the same driver on these systems as well.

Signed-off-by: Florian Fainelli <f.fainelli@gmail.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>