sata: dwc_ahsata: implement sata_port_status

Define the new common function sata_port_status() which can be
used to query the sata driver for the state of ports, and implement it
for dwc_ahsata.

Cc: Stefano Babic <sbabic@denx.de>
Cc: Tom Rini <trini@ti.com>
Cc: Marek Vasut <marex@denx.de>
Reviewed-by: Marek Vasut <marex@denx.de>
Signed-off-by: Nikita Kiryanov <nikita@compulab.co.il>
diff --git a/include/sata.h b/include/sata.h
index c95dc56..38f4b4a 100644
--- a/include/sata.h
+++ b/include/sata.h
@@ -9,6 +9,7 @@
 
 int sata_initialize(void);
 int __sata_initialize(void);
+int sata_port_status(int dev, int port);
 
 extern block_dev_desc_t sata_dev_desc[];