dyndbg-docs: initialization is done early, not arch

since cf964976484 in 2012, initialization is done with early_initcall,
update the Docs, which still say arch_initcall.

Acked-by:  <jbaron@akamai.com>
Signed-off-by: Jim Cromie <jim.cromie@gmail.com>
Link: https://lore.kernel.org/r/20200719231058.1586423-3-jim.cromie@gmail.com


Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>