Detect AMD GPU info via sysfs and block old cards

This wires up some new logic to start using sysfs to discover AMD GPU
information and detects old cards we can't yet support so we can fallback to CPU mode.

gpu/types.go

@@ -16,3 +16,9 @@ type GpuInfo struct {
 
 	// TODO add other useful attributes about the card here for discovery information
 }
+
+type Version struct {
+	Major uint
+	Minor uint
+	Patch uint
+}