doc: update bluetooth to use @option ALIAS

The bluetooth.h header file uses a different tabulation style in the
documentation headers, which for recent Doxygen versions generates
verbatim blocks. This disables usage of the @option ALIAS because
verbatim blocks cannot be nested. With this commit the documentation's
tabulation is fixed and `@option` is used to resolve Kconfig options.

Signed-off-by: Fabio Utzig <fabio.utzig@nordicsemi.no>