hw/mips/boston: don't make flash region 'nomigrate'

Currently we use memory_region_init_rom_nomigrate() to create
the "boston.flash" memory region, and we don't manually register
it with vmstate_register_ram(). This currently means that its
contents are migrated but as a ram block whose name is the empty
string; in future it may mean they are not migrated at all. Use
memory_region_init_ram() instead.

Note that this is a a cross-version migration compatibility break
for the "boston" machine.
Signed-off-by: NPeter Maydell <peter.maydell@linaro.org>
Reviewed-by: NCédric Le Goater <clg@kaod.org>
Reviewed-by: NPhilippe Mathieu-Daudé <f4bug@amsat.org>
Reviewed-by: NPaul Burton <paul.burton@mips.com>
Signed-off-by: NAleksandar Markovic <aleksandar.markovic@mips.com>

hw/mips/boston.c

@@ -471,8 +471,7 @@ static void boston_mach_init(MachineState *machine)
     sysbus_mmio_map_overlap(SYS_BUS_DEVICE(s->cps), 0, 0, 1);
 
     flash =  g_new(MemoryRegion, 1);
-    memory_region_init_rom_nomigrate(flash, NULL,
-                                     "boston.flash", 128 * M_BYTE, &err);
+    memory_region_init_rom(flash, NULL, "boston.flash", 128 * M_BYTE, &err);
     memory_region_add_subregion_overlap(sys_mem, 0x18000000, flash, 0);
 
     ddr = g_new(MemoryRegion, 1);