powerpc/eeh: Cleanup comments in the EEH core

The EEH has been implemented on pSeries platform. The original
code looks a little bit nasty. The patch does cleanup on the
current EEH implementation so that it looks more clean.

        * Duplicated comments have been removed from the corresponding
          header files.
        * Comments have been reorganized so that it looks more clean.
        * The leading comments of functions are adjusted for a little
          bit so that the result of "make pdfdocs" would be more
          unified.
        * Function definitions and calls have unified format as "xxx()".
          That means the format "xxx ()" has been replaced by "xxx()".
        * There're multiple functions implemented for resetting PE. The
          position of those functions have been move around so that they
          are adjacent to each other to reflect their relationship.

Signed-off-by: Gavin Shan <shangw@linux.vnet.ibm.com>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>