powerpc/64s/idle: Fix restore of AMOR on POWER9 after deep sleep

POWER8 restores AMOR when waking from deep sleep, but POWER9 does not,
because it does not go through the subcore restore.

Have POWER9 restore it in core restore.

Fixes: ee97b6b99f ("powerpc/mm/radix: Setup AMOR in HV mode to allow key 0")
Signed-off-by: Nicholas Piggin <npiggin@gmail.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>

arch/powerpc/kernel/idle_book3s.S

@@ -870,6 +870,8 @@ BEGIN_FTR_SECTION
 	mtspr	SPRN_PTCR,r4
 	ld	r4,_RPR(r1)
 	mtspr	SPRN_RPR,r4
+	ld	r4,_AMOR(r1)
+	mtspr	SPRN_AMOR,r4
 END_FTR_SECTION_IFSET(CPU_FTR_ARCH_300)
 
 	ld	r4,_TSCR(r1)