include: Cleanup waffle_error doxygen
include: Cleanup waffle_error doxygen

- Remove redundant comments in waffle_error_get_code().
- Remove references to non-existent function, waffle_finish().

Signed-off-by: Chad Versace <a557f7f75bf28dc19ac99107f5cc7cd6b3fbdb1a@linux.intel.com>

maurossi/waffle,fjhenigman/waffle,chadversary/waffle,evelikov/waffle,waffle-gl/waffle,maurossi/waffle,yinquan529/waffle-gl-waffle,janesma/waffle,dcbaker/waffle,janesma/waffle,maurossi/waffle,chadversary/waffle,fjhenigman/waffle,fjhenigman/waffle,waffle-gl/waffle,dcbaker/waffle,evelikov/waffle,yinquan529/waffle-gl-waffle,dcbaker/waffle,waffle-gl/waffle,evelikov/waffle,janesma/waffle,yinquan529/waffle-gl-waffle,waffle-gl/waffle,chadversary/waffle