kernel/utsname_sysctl.c: replace obsolete __initcall by device_initcall

Also fixes checkpatch warnings on proc_dostring function parameters

Signed-off-by: Fabian Frederick <fabf@skynet.be>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>