initramfs: mount devtmpfs to fix race condition

There is a race condition between mdev creating a device node (notified
by a linux uevent) and the init script mounting /boot.

We are using devtmpfs to fix this problem, as that way the device node
appears inmediately once it is created in kernel space.

initramfs/init

@@ -6,10 +6,9 @@ IMAGEFILE=/boot/imagefile.cpio.gz
 
 
 # Get our basic working environment up.
+mount -t devtmpfs devtmpfs /dev
 mount -t proc proc /proc
 mount -t sysfs sysfs /sys
-mdev -s
-
 
 # This is called if something goes horribly wrong.
 panic()
@@ -276,4 +275,5 @@ sync
 umount /boot
 umount /sys
 umount /proc
+umount /dev
 exec switch_root -c /dev/console /rootfs /sbin/init