kernel/params.c: fix lying comment for param_array()

This fixes the comment for the function param_array. Which lies that it
only *temporarily* mangle the input string @val.

Signed-off-by: Bert Wesarg <wesarg@informatik.uni-halle.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>