Documentation/kbuild: gendwarfksyms: Style cleanup

The indentation in gendwarfksyms.rst currently uses a mix of tabs and
spaces. Convert all indentation to tabs, and match the usage output and
code examples with theirs references.

Suggested-by: Miguel Ojeda <ojeda@kernel.org>
Signed-off-by: Jihan LIN <linjh22s@gmail.com>
Reviewed-by: Petr Pavlu <petr.pavlu@suse.com>
Link: https://patch.msgid.link/20260114-documents_gendwarfksyms-v2-2-297c98bd62c6@gmail.com


[nathan: Minor commit message formatting adjustment]
Signed-off-by: Nathan Chancellor <nathan@kernel.org>