sata: ahci: export ahci_do_hardreset() locally

We need a way to retrieve the information about the online state of
the link in the ahci-da850 driver.

Create a new function: ahci_do_hardreset() which is called from
ahci_hardreset() for backwards compatibility, but has an additional
argument: 'online' - which can be used to check if the link is online
after this function returns.

The new routine will be used in the ahci-da850 driver to avoid code
duplication when implementing a workaround for tha da850 SATA
controller quirk/instability.

Signed-off-by: Bartosz Golaszewski <bgolaszewski@baylibre.com>
Acked-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Sekhar Nori <nsekhar@ti.com>