target/arm: Fix ID_MMFR4 value on AArch64 'max' CPU

In commit 41a4bf1feab098da4cd the added code to set the CNP
field in ID_MMFR4 for the AArch64 'max' CPU had a typo
where it used the wrong variable name, resulting in ID_MMFR4
fields AC2, XNX and LSM being wrong. Fix the typo.

Fixes: 41a4bf1feab098da4cd
Reported-by: Laurent Desnogues <laurent.desnogues@gmail.com>
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Reviewed-by: Edgar E. Iglesias <edgar.iglesias@xilinx.com>
Reviewed-by: Laurent Desnogues <laurent.desnogues@gmail.com>
Message-id: 20200422124501.28015-1-peter.maydell@linaro.org

target/arm/cpu64.c

@@ -705,7 +705,7 @@ static void aarch64_max_initfn(Object *obj)
         u = cpu->isar.id_mmfr4;
         u = FIELD_DP32(u, ID_MMFR4, HPDS, 1); /* AA32HPD */
         u = FIELD_DP32(u, ID_MMFR4, AC2, 1); /* ACTLR2, HACTLR2 */
-        u = FIELD_DP32(t, ID_MMFR4, CNP, 1); /* TTCNP */
+        u = FIELD_DP32(u, ID_MMFR4, CNP, 1); /* TTCNP */
         cpu->isar.id_mmfr4 = u;
 
         u = cpu->isar.id_aa64dfr0;