hw/pci-host: Use memory_region_init_rom() with read-only regions

This commit was produced with the Coccinelle script
scripts/coccinelle/memory-region-housekeeping.cocci.

Acked-by: David Gibson <david@gibson.dropbear.id.au>
Signed-off-by: Philippe Mathieu-Daudé <philmd@redhat.com>

hw/pci-host/prep.c

@@ -325,9 +325,8 @@ static void raven_realize(PCIDevice *d, Error **errp)
     d->config[0x0D] = 0x10; // latency_timer
     d->config[0x34] = 0x00; // capabilities_pointer
 
-    memory_region_init_ram_nomigrate(&s->bios, OBJECT(s), "bios", BIOS_SIZE,
-                           &error_fatal);
-    memory_region_set_readonly(&s->bios, true);
+    memory_region_init_rom_nomigrate(&s->bios, OBJECT(s), "bios", BIOS_SIZE,
+                                     &error_fatal);
     memory_region_add_subregion(get_system_memory(), (uint32_t)(-BIOS_SIZE),
                                 &s->bios);
     if (s->bios_name) {