ata: ahci_brcm: Add back regulators management

While reworking the resources management and departing from using
ahci_platform_enable_resources() which did not allow a proper step
separation like we need, we unfortunately lost the ability to control
AHCI regulators. This broke some Broadcom STB systems that do expect
regulators to be turned on to link up with attached hard drives.

Fixes: c0cdf2ac ("ata: ahci_brcm: Fix AHCI resources management")
Signed-off-by: Florian Fainelli <f.fainelli@gmail.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>