doxygen: refactored doxygen in libbsp/arm/lpc32xx

This patch refactors a lot of the existing doxygen within libbsp/arm/lpc32xx.
Much of this refactoring was just renaming of existing groups to conform to a
more consistent naming structure. With the addition of a doxygen header for
tm27.h, all files within lpc32xx belong to doxygen group now. lpc32xx should
be used a reference for adding doxygen to other bsps.