powerpc/64s/hash: avoid the POWER5 < DD2.1 slb invalidate workaround on POWER8/9

I only have POWER8/9 to test, so just remove it for those.
Signed-off-by: Nicholas Piggin <npiggin@gmail.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>

arch/powerpc/kernel/entry_64.S

@@ -672,7 +672,9 @@ END_MMU_FTR_SECTION_IFSET(MMU_FTR_1T_SEGMENT)
 
 	isync
 	slbie	r6
+BEGIN_FTR_SECTION
 	slbie	r6		/* Workaround POWER5 < DD2.1 issue */
+END_FTR_SECTION_IFCLR(CPU_FTR_ARCH_207S)
 	slbmte	r7,r0
 	isync
 2:

arch/powerpc/mm/slb.c

@@ -326,9 +326,11 @@ void switch_slb(struct task_struct *tsk, struct mm_struct *mm)
 		__slb_flush_and_rebolt();
 	}
 
+	if (!cpu_has_feature(CPU_FTR_ARCH_207S)) {
 		/* Workaround POWER5 < DD2.1 issue */
 		if (offset == 1 || offset > SLB_CACHE_ENTRIES)
 			asm volatile("slbie %0" : : "r" (slbie_data));
+	}
 
 	get_paca()->slb_cache_ptr = 0;
 	copy_mm_to_paca(mm);