riscv: htif: increase the priority of the htif subregion

The htif device is supposed to be mapped over an other subregion. So increase
its priority to one to avoid any conflict.

Here is the output of info mtree:

Before:
(qemu) info mtree
 address-space: memory
   0000000000000000-ffffffffffffffff (prio 0, i/o): system
     0000000000000000-000000000000000f (prio 0, i/o): riscv.htif.uart
     0000000000000000-0000000000011fff (prio 0, ram): riscv.spike.bootrom
     0000000002000000-000000000200ffff (prio 0, i/o): riscv.sifive.clint
     0000000080000000-0000000087ffffff (prio 0, ram): riscv.spike.ram

 address-space: I/O
   0000000000000000-000000000000ffff (prio 0, i/o): io

 address-space: cpu-memory-0
   0000000000000000-ffffffffffffffff (prio 0, i/o): system
     0000000000000000-000000000000000f (prio 0, i/o): riscv.htif.uart
     0000000000000000-0000000000011fff (prio 0, ram): riscv.spike.bootrom
     0000000002000000-000000000200ffff (prio 0, i/o): riscv.sifive.clint
     0000000080000000-0000000087ffffff (prio 0, ram): riscv.spike.ram

After:
 (qemu) info mtree
 address-space: memory
   0000000000000000-ffffffffffffffff (prio 0, i/o): system
     0000000000000000-000000000000000f (prio 1, i/o): riscv.htif.uart
     0000000000000000-0000000000011fff (prio 0, ram): riscv.spike.bootrom
     0000000002000000-000000000200ffff (prio 0, i/o): riscv.sifive.clint
     0000000080000000-0000000087ffffff (prio 0, ram): riscv.spike.ram

 address-space: I/O
   0000000000000000-000000000000ffff (prio 0, i/o): io

 address-space: cpu-memory-0
   0000000000000000-ffffffffffffffff (prio 0, i/o): system
     0000000000000000-000000000000000f (prio 1, i/o): riscv.htif.uart
     0000000000000000-0000000000011fff (prio 0, ram): riscv.spike.bootrom
     0000000002000000-000000000200ffff (prio 0, i/o): riscv.sifive.clint
     0000000080000000-0000000087ffffff (prio 0, ram): riscv.spike.ram
Reviewed-by: NMichael Clark <mjc@sifive.com>
Signed-off-by: NKONRAD Frederic <frederic.konrad@adacore.com>
Signed-off-by: NMichael Clark <mjc@sifive.com>

Message-Id: <1525360636-18229-3-git-send-email-frederic.konrad@adacore.com>

hw/riscv/riscv_htif.c

@@ -253,8 +253,9 @@ HTIFState *htif_mm_init(MemoryRegion *address_space, MemoryRegion *main_mem,
         htif_be_change, s, NULL, true);
     if (address_symbol_set == 3) {
         memory_region_init_io(&s->mmio, NULL, &htif_mm_ops, s,
-                            TYPE_HTIF_UART, size);
-        memory_region_add_subregion(address_space, base, &s->mmio);
+                              TYPE_HTIF_UART, size);
+        memory_region_add_subregion_overlap(address_space, base,
+                                            &s->mmio, 1);
     }
 
     return s;