dt-bindings: ata: rename brcm, sata-brcmstb.txt to brcm, sata-brcm.txt

Renames the dt bindings document of Broadcom STB ahci driver to
common Broadcom ahci driver bindings document
Signed-off-by: Yendapally Reddy Dhananjaya Reddy <yendapally.reddy@broadcom.com>
Acked-by: Florian Fainelli <f.fainelli@gmail.com>
Signed-off-by: Tejun Heo <tj@kernel.org>

Documentation/devicetree/bindings/ata/brcm,sata-brcmstb.txt → Documentation/devicetree/bindings/ata/brcm,sata-brcm.txt

-* Broadcom SATA3 AHCI Controller for STB
+* Broadcom SATA3 AHCI Controller
 
 SATA nodes are defined to describe on-chip Serial ATA controllers.
 Each SATA controller should have its own node.