uml: fix vde network backend in user mode linux

* Replace kmalloc() with uml_kmalloc() (fix build failure)

* Remove unnecessary UM_KERN_INFO in printk() (don't display '<6>' while
  printing info)

Signed-off-by: Luca Bigliardi <shammash@artha.org>
Cc: Jiri Kosina <jkosina@suse.cz>
Reviewed-by: WANG Cong <wangcong@zeuux.org>
Cc: Jeff Dike <jdike@addtoit.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>