Report the capability of vaCopy support

Report vaCopy support, it is a standalone feature , which is related with vaDisplay. not depend on VPP , vaConfig etc.

Signed-off-by: Carl Zhang <carl.zhang@intel.com>
diff --git a/va/va.h b/va/va.h
index f24e7c4..e9c0b21 100644
--- a/va/va.h
+++ b/va/va.h
@@ -5056,6 +5056,12 @@
      * HW attribute, read/write, specify the sub device configure
      */
     VADisplayAttribSubDevice           = 19,
+    /*
+     * HW attribute. read only. specify whether vaCopy support on current HW
+     * The value of each bit should equal to 1 << VA_EXEC_MODE_XXX to represent
+     * modes of vaCopy
+     */
+    VADisplayAttribCopy                 = 20,
 } VADisplayAttribType;
 
 /* flags for VADisplayAttribute */