ata: ahci_brcm: Allow optional reset controller to be used

commit 2b2c47d9 upstream.

On BCM63138, we need to reset the AHCI core prior to start utilizing it,
grab the reset controller device cookie and do that.

Signed-off-by: Florian Fainelli <f.fainelli@gmail.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>