udev: Cut down default /dev tmpfs size from 10Mb to 2Mb, to preclude DoS.

udev: Cut down default /dev tmpfs size from 10Mb to 2Mb, to preclude DoS.
* Like ramdisk the stupid script spit tens of megabytes to a "device",
without checking if it exists.
* Generall, /dev should contains only devices, typical size - tens of Kb.