powerpc/configs: Add LIBNVDIMM to ppc64_defconfig

This gives us OF_PMEM which is useful in mambo.

This adds 153K to the text of ppc64le_defconfig which 0.8% of the
total text.

  LIBNVDIMM text     data    bss     dec      hex
  Without   18574833 5518150 1539240 25632223 1871ddf
  With      18727834 5546206 1539368 25813408 189e1a0
Signed-off-by: Michael Neuling <mikey@neuling.org>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20200519043009.3081885-1-mikey@neuling.org

arch/powerpc/configs/ppc64_defconfig

@@ -281,6 +281,7 @@ CONFIG_RTC_CLASS=y
 CONFIG_RTC_DRV_DS1307=y
 CONFIG_VIRTIO_PCI=m
 CONFIG_VIRTIO_BALLOON=m
+CONFIG_LIBNVDIMM=y
 CONFIG_RAS=y
 CONFIG_EXT2_FS=y
 CONFIG_EXT2_FS_XATTR=y