aarch64: Create QL_SRC_X2 and QL_DEST_X2 qualifier macros

Some 128-bit system operations (mrrs, msrr, tlbip, and sysp) take two
qualified operands and one of unqualified type (e.g. system register
name, tlbip operation).  This creates the need for adequate qualifiers
to handle this.

This patch therefore introduces the `QL_SRC_X2' and `QL_DST_X2' qualifier
specifiers, which expand to `QLF3(NIL,X,X)' and `QLF3(X,X,NIL)',
respectively.

opcodes/aarch64-tbl.h

@@ -52,12 +52,24 @@
   QLF2(NIL,X),			\
 }
 
+/* e.g. MSRR <systemreg>, <Xt>, <Xt2>.  */
+#define QL_SRC_X2		\
+{				\
+  QLF3(NIL,X,X),		\
+}
+
 /* e.g. MRS <Xt>, <systemreg>.  */
 #define QL_DST_X		\
 {				\
   QLF2(X,NIL),			\
 }
 
+/* e.g. MRRS <Xt>, <Xt2>, <systemreg>.  */
+#define QL_DST_X2		\
+{				\
+  QLF3(X,X,NIL),		\
+}
+
 /* e.g. SYS #<op1>, <Cn>, <Cm>, #<op2>{, <Xt>}.  */
 #define QL_SYS			\
 {				\