powerpc: Add MTD_BLOCK to powernv_defconfig

This is so we can use the powernv_flash mtd driver as an block
device.
Signed-off-by: Michael Neuling <mikey@neuling.org>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>

arch/powerpc/configs/powernv_defconfig

@@ -80,6 +80,7 @@ CONFIG_UEVENT_HELPER_PATH="/sbin/hotplug"
 CONFIG_DEVTMPFS=y
 CONFIG_DEVTMPFS_MOUNT=y
 CONFIG_MTD=y
+CONFIG_MTD_BLOCK=y
 CONFIG_MTD_POWERNV_FLASH=y
 CONFIG_PARPORT=m
 CONFIG_PARPORT_PC=m