target/arm: Update define_one_arm_cp_reg_with_opaque for VHE

For ARMv8.1, op1 == 5 is reserved for EL2 aliases of
EL1 and EL0 registers.

Tested-by: Alex Bennée <alex.bennee@linaro.org>
Reviewed-by: Peter Maydell <peter.maydell@linaro.org>
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
Message-id: 20200206105448.4726-28-richard.henderson@linaro.org
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>

target/arm/helper.c

@@ -7586,13 +7586,10 @@ void define_one_arm_cp_reg_with_opaque(ARMCPU *cpu,
             mask = PL0_RW;
             break;
         case 4:
+        case 5:
             /* min_EL EL2 */
             mask = PL2_RW;
             break;
-        case 5:
-            /* unallocated encoding, so not possible */
-            assert(false);
-            break;
         case 6:
             /* min_EL EL3 */
             mask = PL3_RW;