[committed] libgomp/testsuite/libgomp.oacc-fortran: Update dg-output to fix GCN

[Tobias Burnus]

The comment in the patch give the reason, why that line is missing with 
AMDGCN (and nvptx). – For the extra line of nvptx, see referenced PR 
(last comment).

Applied as Rev. 278986 after testing w/o offloading configured and with 
nvptx + amdgcn offloading.

Cheers,

Tobias