LoongArch: Move __arch_cpu_idle() to .cpuidle.text section

Now arch_cpu_idle() is annotated with __cpuidle which means it is in
the .cpuidle.text section, but __arch_cpu_idle() isn't. Thus, fix the
missing .cpuidle.text section assignment for __arch_cpu_idle() in order
to correct backtracing with nmi_backtrace().

The principle is similar to the commit 97c8580 ("MIPS: Annotate
cpu_wait implementations with __cpuidle")

Cc: stable@vger.kernel.org
Signed-off-by: Huacai Chen <chenhuacai@loongson.cn>

arch/loongarch/kernel/genex.S

@@ -16,6 +16,7 @@
 #include <asm/stackframe.h>
 #include <asm/thread_info.h>
 
+	.section .cpuidle.text, "ax"
 	.align	5
 SYM_FUNC_START(__arch_cpu_idle)
 	/* start of idle interrupt region */
@@ -31,14 +32,16 @@ SYM_FUNC_START(__arch_cpu_idle)
 	 */
 	idle	0
 	/* end of idle interrupt region */
-1:	jr	ra
+idle_exit:
+	jr	ra
 SYM_FUNC_END(__arch_cpu_idle)
+	.previous
 
 SYM_CODE_START(handle_vint)
 	UNWIND_HINT_UNDEFINED
 	BACKUP_T0T1
 	SAVE_ALL
-	la_abs	t1, 1b
+	la_abs	t1, idle_exit
 	LONG_L	t0, sp, PT_ERA
 	/* 3 instructions idle interrupt region */
 	ori	t0, t0, 0b1100