kbuild: split adjust_autoksyms.sh in two parts

kbuild: split adjust_autoksyms.sh in two parts

In order to prepare the ground for a build-time optimization, split
adjust_autoksyms.sh into two scripts: one that generates autoksyms.h
based on all currently available information (whitelist, and .mod
files), and the other to inspect the diff between two versions of
autoksyms.h and trigger appropriate rebuilds.

Acked-by: Nicolas Pitre <[email protected]>
Tested-by: Matthias Maennich <[email protected]>
Reviewed-by: Matthias Maennich <[email protected]>
Signed-off-by: Quentin Perret <[email protected]>
Signed-off-by: Masahiro Yamada <[email protected]>