arm/imx25_pdk: 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>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Message-Id: <20200219160953.13771-17-imammedo@redhat.com>

hw/arm/imx25_pdk.c

@@ -59,7 +59,6 @@
 
 typedef struct IMX25PDK {
     FslIMX25State soc;
-    MemoryRegion ram;
     MemoryRegion ram_alias;
 } IMX25PDK;
 
@@ -86,10 +85,8 @@ static void imx25_pdk_init(MachineState *machine)
         exit(EXIT_FAILURE);
     }
 
-    memory_region_allocate_system_memory(&s->ram, NULL, "imx25.ram",
-                                         machine->ram_size);
     memory_region_add_subregion(get_system_memory(), FSL_IMX25_SDRAM0_ADDR,
-                                &s->ram);
+                                machine->ram);
 
     /* initialize the alias memory if any */
     for (i = 0, ram_size = machine->ram_size, alias_offset = 0;
@@ -109,7 +106,8 @@ static void imx25_pdk_init(MachineState *machine)
 
         if (size < ram[i].size) {
             memory_region_init_alias(&s->ram_alias, NULL, "ram.alias",
-                                     &s->ram, alias_offset, ram[i].size - size);
+                                     machine->ram,
+                                     alias_offset, ram[i].size - size);
             memory_region_add_subregion(get_system_memory(),
                                         ram[i].addr + size, &s->ram_alias);
         }
@@ -137,6 +135,7 @@ static void imx25_pdk_machine_init(MachineClass *mc)
     mc->desc = "ARM i.MX25 PDK board (ARM926)";
     mc->init = imx25_pdk_init;
     mc->ignore_memory_transaction_failures = true;
+    mc->default_ram_id = "imx25.ram";
 }
 
 DEFINE_MACHINE("imx25-pdk", imx25_pdk_machine_init)