[PATCH] Fix device_attribute memory leak in device_del

dev->devt_attr is allocated in device_add() but it is never freed in
device_del() in the drivers/base/core.c file (reported by kmemleak).

Signed-off-by: Catalin Marinas <catalin.marinas@gmail.com>
Acked-by: Greg KH <greg@kroah.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>