target-microblaze: mmu: Add a configurable output address mask

Add a configurable output address mask, used to mimic the
configurable physical address bit width.

Reviewed-by: Alistair Francis <alistair.francis@wdc.com>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Signed-off-by: Edgar E. Iglesias <edgar.iglesias@xilinx.com>

target/microblaze/cpu.c

@@ -128,6 +128,7 @@ static void mb_cpu_reset(CPUState *s)
     env->mmu.c_mmu = 3;
     env->mmu.c_mmu_tlb_access = 3;
     env->mmu.c_mmu_zones = 16;
+    env->mmu.c_addr_mask = MAKE_64BIT_MASK(0, cpu->cfg.addr_size);
 #endif
 }