powerpc: On POWERNV enable PPC_DENORMALISATION by default

We want PPC_DENORMALISATION enabled when POWERNV is enabled,
so update the Kconfig.
Signed-off-by: NAnton Blanchard <anton@samba.org>
Acked-by: NMichael Neuling <mikey@neuling.org>
Signed-off-by: NBenjamin Herrenschmidt <benh@kernel.crashing.org>
CC: <stable@vger.kernel.org>

arch/powerpc/Kconfig

@@ -566,7 +566,7 @@ config SCHED_SMT
 config PPC_DENORMALISATION
 	bool "PowerPC denormalisation exception handling"
 	depends on PPC_BOOK3S_64
-	default "n"
+	default "y" if PPC_POWERNV
 	---help---
 	  Add support for handling denormalisation of single precision
 	  values.  Useful for bare metal only.  If unsure say Y here.