powerpc/64s: Make flush_and_reload_slb a no-op when radix is enabled

The radix test can exclude slb_flush_all_realmode() from being called
because flush_and_reload_slb() is only expected to flush ERAT when
called by flush_erat(), which is only on pre-ISA v3.0 CPUs that do not
support radix.

This helps the later change to make hash support configurable to not
introduce runtime changes to radix mode behaviour.
Signed-off-by: Nicholas Piggin <npiggin@gmail.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20211201144153.2456614-9-npiggin@gmail.com

arch/powerpc/kernel/mce_power.c

@@ -80,12 +80,12 @@ static bool mce_in_guest(void)
 #ifdef CONFIG_PPC_BOOK3S_64
 void flush_and_reload_slb(void)
 {
-	/* Invalidate all SLBs */
-	slb_flush_all_realmode();
-
 	if (early_radix_enabled())
 		return;
 
+	/* Invalidate all SLBs */
+	slb_flush_all_realmode();
+
 	/*
 	 * This probably shouldn't happen, but it may be possible it's
 	 * called in early boot before SLB shadows are allocated.