xen/arm: get privilege status

Use Xen features to figure out if we are privileged.

XENFEAT_dom0 was introduced by 23735 in xen-unstable.hg.

Signed-off-by: Stefano Stabellini <stefano.stabellini@eu.citrix.com>
Acked-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>

include/xen/interface/features.h

@@ -50,6 +50,9 @@
 /* x86: pirq can be used by HVM guests */
 #define XENFEAT_hvm_pirqs           10
 
+/* operation as Dom0 is supported */
+#define XENFEAT_dom0                      11
+
 #define XENFEAT_NR_SUBMAPS 1
 
 #endif /* __XEN_PUBLIC_FEATURES_H__ */