Enable DEVTMPFS for Fedora 15

[DJ Delorie]

One of possibly many kernel config changes to support Fedora 15.  This
one is required to at least boot.

--- a/arch/arm/configs/xo_175_defconfig	2011-09-09 16:50:12.000000000 -0400
+++ b/arch/arm/configs/xo_175_defconfig	2011-09-09 18:20:21.000000000 -0400
@@ -536,5 +538,6 @@
 #
 CONFIG_UEVENT_HELPER_PATH=""
-# CONFIG_DEVTMPFS is not set
+CONFIG_DEVTMPFS=y
+CONFIG_DEVTMPFS_MOUNT=y
 # CONFIG_STANDALONE is not set
 # CONFIG_PREVENT_FIRMWARE_BUILD is not set