LoongArch: Use UNWIND_HINT_END_OF_STACK for entry points

kernel_entry() and smpboot_entry() are the last frames for ORC unwinder,
so it is proper to use the annotation UNWIND_HINT_END_OF_STACK for them.

Link: https://lore.kernel.org/lkml/ots6w2ntyudj5ucs5eowncta2vmfssatpcqwzpar3ekk577hxi@j45dd4dmwx6x/
Suggested-by: Josh Poimboeuf <jpoimboe@kernel.org>
Signed-off-by: Tiezhu Yang <yangtiezhu@loongson.cn>
Signed-off-by: Huacai Chen <chenhuacai@loongson.cn>

Author: seehearfeel

arch/loongarch/kernel/head.S

@@ -42,6 +42,7 @@ SYM_DATA(kernel_fsize, .long _kernel_fsize);
 	.align 12
 
 SYM_CODE_START(kernel_entry)			# kernel entry point
+	UNWIND_HINT_END_OF_STACK
 
 	SETUP_TWINS
 	SETUP_MODES	t0
@@ -113,6 +114,7 @@ SYM_CODE_END(kernel_entry)
  * function after setting up the stack and tp registers.
  */
 SYM_CODE_START(smpboot_entry)
+	UNWIND_HINT_END_OF_STACK
 
 	SETUP_TWINS
 	SETUP_MODES	t0