MIPS: OCTEON: Enable DEVTMPFS

Recent versions of udev and systemd require the kernel to be compiled
with CONFIG_DEVTMPFS in order to populate the /dev directory. Most MIPS
platforms have it enabled by default, so enable it for the Cavium Octeon
defconfig as well. This will assist with automated kernel boot testing.
Signed-off-by: James Hogan <james.hogan@imgtec.com>
Acked-by: David Daney <david.daney@cavium.com>
Cc: Ralf Baechle <ralf@linux-mips.org>
Cc: linux-mips@linux-mips.org
Patchwork: https://patchwork.linux-mips.org/patch/15294/Signed-off-by: James Hogan <james.hogan@imgtec.com>

arch/mips/configs/cavium_octeon_defconfig

@@ -45,6 +45,7 @@ CONFIG_SYN_COOKIES=y
 # CONFIG_INET_LRO is not set
 CONFIG_IPV6=y
 CONFIG_UEVENT_HELPER_PATH="/sbin/hotplug"
+CONFIG_DEVTMPFS=y
 # CONFIG_FW_LOADER is not set
 CONFIG_MTD=y
 # CONFIG_MTD_OF_PARTS is not set