target/alpha: Remove fallback to ev67 cpu class

'ev67' CPU class will be returned to match everything, which makes
no sense as mentioned in the comments. Remove the logic to fall
back to 'ev67' CPU class to match everything.

Signed-off-by: Gavin Shan <gshan@redhat.com>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Reviewed-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Message-ID: <20231114235628.534334-2-gshan@redhat.com>
[PMD: Reword subject, replace 'any' -> 'ev67' on linux-user]
Signed-off-by: Philippe Mathieu-Daudé <philmd@linaro.org>

linux-user/alpha/target_elf.h

@@ -9,6 +9,6 @@
 #define ALPHA_TARGET_ELF_H
 static inline const char *cpu_get_model(uint32_t eflags)
 {
-    return "any";
+    return "ev67";
 }
 #endif

target/alpha/cpu.c

@@ -141,11 +141,8 @@ static ObjectClass *alpha_cpu_class_by_name(const char *cpu_model)
     typename = g_strdup_printf(ALPHA_CPU_TYPE_NAME("%s"), cpu_model);
     oc = object_class_by_name(typename);
     g_free(typename);
-
-    /* TODO: remove match everything nonsense */
-    if (!oc || object_class_is_abstract(oc)) {
-        /* Default to ev67; no reason not to emulate insns by default. */
-        oc = object_class_by_name(ALPHA_CPU_TYPE_NAME("ev67"));
+    if (!oc || !object_class_dynamic_cast(oc, TYPE_ALPHA_CPU)) {
+        return NULL;
     }
 
     return oc;