openocd: fix incorrect doxygen comments

openocd: fix incorrect doxygen comments

Use '@param' in front of function's parameters and '@a' when the
parameter is recalled in the description.

This fixes doxygen complains:
	warning: Found unknown command '@buff16'

While there, fix a minor typo s/occured/occurred/ in a comment and
the typo s/@apram/@param/ in a doxygen comment.

Change-Id: I5cd86a80adef552331310a21c55ec5d11354be21
Signed-off-by: Antonio Borneo <borneo.antonio@gmail.com>
Reviewed-on: http://openocd.zylin.com/6001
Tested-by: jenkins