powerpc/powernv: remove orphan declarations from opal.h

Remove the following orphan declarations from opal.h:
1. opal_notifier_register()
2. opal_notifier_unregister()
3. opal_notifier_update_evt()
4. opal_notifier_enable()
5. opal_notifier_disable()

They have been removed since commit 81f2f7ce ("opal:
Remove events notifier"), so remove them.
Signed-off-by: Gaosheng Cui <cuigaosheng1@huawei.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20220913075029.682327-7-cuigaosheng1@huawei.com

arch/powerpc/include/asm/opal.h

@@ -324,16 +324,10 @@ extern int opal_flush_console(uint32_t vtermno);
 
 extern void hvc_opal_init_early(void);
 
-extern int opal_notifier_register(struct notifier_block *nb);
-extern int opal_notifier_unregister(struct notifier_block *nb);
-
 extern int opal_message_notifier_register(enum opal_msg_type msg_type,
 						struct notifier_block *nb);
 extern int opal_message_notifier_unregister(enum opal_msg_type msg_type,
 					    struct notifier_block *nb);
-extern void opal_notifier_enable(void);
-extern void opal_notifier_disable(void);
-extern void opal_notifier_update_evt(uint64_t evt_mask, uint64_t evt_val);
 
 extern int opal_async_get_token_interruptible(void);
 extern int opal_async_release_token(int token);