sata: ahci-da850: get the sata clock using a connection id

In preparation for using two clocks in the driver (the sysclk2-based
clock and the external REFCLK), check if we got the functional clock
after calling ahci_platform_get_resources(). If not, retry calling
clk_get() with con_id specified.

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