mips/mips_fulong2e: use memdev for RAM

memory_region_allocate_system_memory() API is going away, so
replace it with memdev allocated MemoryRegion. The later is
initialized by generic code, so board only needs to opt in
to memdev scheme by providing
  MachineClass::default_ram_id
and using MachineState::ram instead of manually initializing
RAM memory region.

Signed-off-by: Igor Mammedov <imammedo@redhat.com>
Reviewed-by: Philippe Mathieu-Daudé <philmd@redhat.com>
Message-Id: <20200219160953.13771-53-imammedo@redhat.com>

hw/mips/mips_fulong2e.c

@@ -294,7 +294,6 @@ static void mips_fulong2e_init(MachineState *machine)
     const char *initrd_filename = machine->initrd_filename;
     char *filename;
     MemoryRegion *address_space_mem = get_system_memory();
-    MemoryRegion *ram = g_new(MemoryRegion, 1);
     MemoryRegion *bios = g_new(MemoryRegion, 1);
     long bios_size;
     uint8_t *spd_data;
@@ -320,13 +319,11 @@ static void mips_fulong2e_init(MachineState *machine)
     }
 
     /* allocate RAM */
-    memory_region_allocate_system_memory(ram, NULL, "fulong2e.ram",
-                                         machine->ram_size);
     memory_region_init_ram(bios, NULL, "fulong2e.bios", BIOS_SIZE,
                            &error_fatal);
     memory_region_set_readonly(bios, true);
 
-    memory_region_add_subregion(address_space_mem, 0, ram);
+    memory_region_add_subregion(address_space_mem, 0, machine->ram);
     memory_region_add_subregion(address_space_mem, 0x1fc00000LL, bios);
 
     /*
@@ -402,6 +399,7 @@ static void mips_fulong2e_machine_init(MachineClass *mc)
     mc->block_default_type = IF_IDE;
     mc->default_cpu_type = MIPS_CPU_TYPE_NAME("Loongson-2E");
     mc->default_ram_size = 256 * MiB;
+    mc->default_ram_id = "fulong2e.ram";
 }
 
 DEFINE_MACHINE("fulong2e", mips_fulong2e_machine_init)