Various Doxygen-related fixes in libpayload (trivial).

Various Doxygen-related fixes in libpayload (trivial).

 - Drop all '@brief's, they're not needed as we use JAVADOC_AUTOBRIEF.
   The first sentence of every description will be treated as the '@brief'
   automatically.

 - Also, put all documentation/descriptions on top of the Doxygen-comments,
   and put the '@foo' keywords at the bottom of the comments for consistency.

 - Change comments for SEEK_SET/SEEK_CUR/SEEK_END from '/**@def' to '/**<'
   in order to make them appear in the output.

 - Drop all explicit '@struct' lines (which are optional; Doxygen will figure
   out that it's a struct if the comment is right before the struct).

 - Fix various typos, whitespace issues, etc.

 - Fix incorrect @param variable names, e.g. change '@param n foobar' to
   '@param s foobar' if the variable is named 's'.

Signed-off-by: Uwe Hermann <uwe@hermann-uwe.de>
Acked-by: Uwe Hermann <uwe@hermann-uwe.de>
git-svn-id: svn://svn.coreboot.org/coreboot/trunk@3555 2b7e53f0-3cfb-0310-b3e9-8179ed1497e1