target-arm/helper.c: Allow const opaques in arm CP

Allow for defining const opaque data in ARM CP register definitions by
setting .opaque = foo. If non null opaque is passed into
define_one_arm_cp_reg_with_opaque then that opaque will take
precedence, otherwise if null opaque is passed, the original opaque
data will be used.

Signed-off-by: Peter Crosthwaite <peter.crosthwaite@xilinx.com>
Message-id: cf0a3ac3438d97464240db9f5f4ef1585cbc1d77.1373429432.git.peter.crosthwaite@xilinx.com
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>

target-arm/helper.c

@@ -1608,7 +1608,9 @@ void define_one_arm_cp_reg_with_opaque(ARMCPU *cpu,
                 ARMCPRegInfo *r2 = g_memdup(r, sizeof(ARMCPRegInfo));
                 int is64 = (r->type & ARM_CP_64BIT) ? 1 : 0;
                 *key = ENCODE_CP_REG(r->cp, is64, r->crn, crm, opc1, opc2);
-                r2->opaque = opaque;
+                if (opaque) {
+                    r2->opaque = opaque;
+                }
                 /* Make sure reginfo passed to helpers for wildcarded regs
                  * has the correct crm/opc1/opc2 for this reg, not CP_ANY:
                  */