powerpc/rtas: Make enter_rtas a nokprobe symbol on 64-bit

This symbol is marked nokprobe on 32-bit but not 64-bit, add it.
Signed-off-by: Nicholas Piggin <npiggin@gmail.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20220308135047.478297-3-npiggin@gmail.com

arch/powerpc/kernel/rtas_entry.S

@@ -164,6 +164,7 @@ rtas_return_loc:
 	mtspr	SPRN_SRR1,r4
 	RFI_TO_KERNEL
 	b	.	/* prevent speculative execution */
+_ASM_NOKPROBE_SYMBOL(enter_rtas)
 _ASM_NOKPROBE_SYMBOL(__enter_rtas)
 _ASM_NOKPROBE_SYMBOL(rtas_return_loc)