hw/sparc: Implement fw_cfg_arch_key_name()

Implement fw_cfg_arch_key_name(), which returns the name of a
sparc32-specific key.

Reviewed-by: Laszlo Ersek <lersek@redhat.com>
Message-Id: <20190422195020.1494-7-philmd@redhat.com>
Signed-off-by: Philippe Mathieu-Daudé <philmd@redhat.com>

hw/sparc/sun4m.c

@@ -97,6 +97,25 @@ struct sun4m_hwdef {
     uint8_t nvram_machine_id;
 };
 
+const char *fw_cfg_arch_key_name(uint16_t key)
+{
+    static const struct {
+        uint16_t key;
+        const char *name;
+    } fw_cfg_arch_wellknown_keys[] = {
+        {FW_CFG_SUN4M_DEPTH, "depth"},
+        {FW_CFG_SUN4M_WIDTH, "width"},
+        {FW_CFG_SUN4M_HEIGHT, "height"},
+    };
+
+    for (size_t i = 0; i < ARRAY_SIZE(fw_cfg_arch_wellknown_keys); i++) {
+        if (fw_cfg_arch_wellknown_keys[i].key == key) {
+            return fw_cfg_arch_wellknown_keys[i].name;
+        }
+    }
+    return NULL;
+}
+
 static void fw_cfg_boot_set(void *opaque, const char *boot_device,
                             Error **errp)
 {