libgomp.texi: List GCN's 'gfx803' under OpenMP Context Selectors

libgomp/ChangeLog:

	* libgomp.texi (OpenMP Context Selectors): Add 'gfx803' to gcn's isa.

diff --git a/libgomp/libgomp.texi b/libgomp/libgomp.texi
index 85cae742cd4..0066d41fdc5 100644
--- a/libgomp/libgomp.texi
+++ b/libgomp/libgomp.texi
@@ -4378,5 +4378,6 @@ offloading devices (it's not clear if they should be):
 @item @code{amdgcn}, @code{gcn}
       @tab @code{gpu}
-      @tab See @code{-march=} in ``AMD GCN Options''
+      @tab See @code{-march=} in ``AMD GCN Options''@footnote{Additionally
+      supported is @code{gfx803} as an alias for @code{fiji}.}
 @item @code{nvptx}
       @tab @code{gpu}