Merged in raiden00/nuttx (pull request #477)

Master

* stm32f33xxx_hrtim.h: add some comments

* stm32_hrtim: add burst mode configuration, rename some definitions

* smps.h: add private data to the smps_s structure

* stm32_hrtim: cosmetics

Approved-by: Gregory Nutt <gnutt@nuttx.org>