Documentation: move init-hook usage from kernel code
start: fix unmatched CONFIG_DEBUG condition

Signed-off-by: Jim Huang <jserv@0xlab.org>
start: inline the memory helper functions
use explicit name run_init_hook rather than init_hook

macro INIT_HOOK is used for register the runlevel and order for certain
initialization process. Avoiding the name confusion, the runner is renamed
to run_init_hook.
Fix compile error while "Tickless scheduling" is opened but "Track tickless scheduling status" is closed.