powerpc: Fix merge conflict between pcrel and copy_thread changes

Fix a conflict between commit 4e991e3c ("powerpc: add CFUNC
assembly label annotation") and commit b504b6aa ("powerpc:
differentiate kthread from user kernel thread start").

Fixes: 4e991e3c ("powerpc: add CFUNC assembly label annotation")
Fixes: b504b6aa ("powerpc: differentiate kthread from user kernel thread start")
Signed-off-by: Nicholas Piggin <npiggin@gmail.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://msgid.link/20230426055848.402993-2-npiggin@gmail.com

arch/powerpc/kernel/interrupt_64.S

@@ -756,7 +756,7 @@ _GLOBAL(ret_from_kernel_user_thread)
 	b	.Lsyscall_exit
 
 _GLOBAL(start_kernel_thread)
-	bl	schedule_tail
+	bl	CFUNC(schedule_tail)
 	mtctr	r14
 	mr	r3,r15
 #ifdef CONFIG_PPC64_ELF_ABI_V2