linux/kernel.h: fix kernel-doc warning

Fix kernel-doc warning in <linux/kernel.h>:

  Warning(include/linux/kernel.h:590): No description found for parameter 'ip'

scripts/kernel-doc cannot handle macros, functions, or function
prototypes between the function or macro that is being documented and
its definition, so move these prototypes above the function that is
being documented.

Signed-off-by: Randy Dunlap <rdunlap@infradead.org>
Cc: Steven Rostedt <rostedt@goodmis.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>