AMD Fam16: Add OSC method to PCI0

The _OSC method is used to tell the OS what capabilities it can
take control over from the firmware.  This method is described
in chapter 6.2.9 of the ACPI spec v3.0.  The method takes 4
inputs (UUID, Rev ID, Input Count, and Capabilities Buffer) and
returns a Capabilites Buffer the same size as the input Buffer.
This Buffer is generally 3 Dwords long consisting of an Errors
Dword, a Supported Capabilities Dword, and a Control Dword.
The OS will request control of certain capabilities and the
firmware must grant or deny control of those features.  We do not
want to have control over anything so let the OS control as much
as it can.

The _OSC method is required for PCIe devices.  During Linux boot,
an error is logged to dmesg if _OSC is not found.

Change-Id: Icf6e7a82284d03d23fd30ee7b7db17754e988c9a
Signed-off-by: Mike Loptien <mike.loptien@se-eng.com>
Reviewed-on: http://review.coreboot.org/3823
Tested-by: build bot (Jenkins)
Reviewed-by: Paul Menzel <paulepanter@users.sourceforge.net>

src/southbridge/amd/agesa/hudson/acpi/fch.asl

@@ -21,6 +21,25 @@
 /* South Bridge */
 /*  _SB.PCI0 */
 
+/* Operating System Capabilities Method */
+Method(_OSC,4)
+{
+	// Create DWord-addressable fields from the Capabilities Buffer
+	CreateDWordField(Arg3,0,CDW1)
+	CreateDWordField(Arg3,4,CDW2)
+	CreateDWordField(Arg3,8,CDW3)
+
+	/* Check for proper PCI/PCIe UUID */
+	If(LEqual(Arg0,ToUUID("33DB4D5B-1FF7-401C-9657-7441C03DD766")))
+	{
+		/* Let OS control everything */
+		Return (Arg3)
+	} Else {
+		Or(CDW1,4,CDW1)	// Unrecognized UUID
+		Return(Arg3)
+	}
+}
+
 /* Describe the Southbridge devices */
 
 /* 0:11.0 - SATA */