sata: ahci-da850: implement a workaround for the softreset quirk

There's an issue with the da850 SATA controller: if port multiplier
support is compiled in, but we're connecting the drive directly to
the SATA port on the board, the drive can't be detected.

To make SATA work on the da850-lcdk board: first try to softreset
with pmp - if the operation fails with -EBUSY, retry without pmp.

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