kbuild: deb-pkg: use build ID instead of debug link for dbg package

There are two ways of managing separate debug info files:

 [1] The executable contains the .gnu_debuglink section, which specifies
     the name and the CRC of the separate debug info file.

 [2] The executable contains a build ID, and the corresponding debug info
     file is placed in the .build-id directory.

We could do both, but the former, which 'make deb-pkg' currently does,
results in complicated installation steps because we need to manually
strip the debug sections, create debug links, and re-sign the modules.
Besides, it is not working with module compression.

This commit abandons the approach [1], and instead opts for [2].

Debian kernel commit de26137e2a9f ("Drop not needed extra step to add
debug links") also stopped adding debug links.

Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>