radv: fix compiler issues with GCC 9

radv: fix compiler issues with GCC 9

"The C standard says that compound literals which occur inside of
the body of a function have automatic storage duration associated
with the enclosing block. Older GCC releases were putting such
compound literals into the scope of the whole function, so their
lifetime actually ended at the end of containing function. This
has been fixed in GCC 9. Code that relied on this extended lifetime
needs to be fixed, move the compound literals to whatever scope
they need to accessible in."

Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=109543
Cc: <mesa-stable@lists.freedesktop.org>
Signed-off-by: Samuel Pitoiset <samuel.pitoiset@gmail.com>
Reviewed-by: Gustaw Smolarczyk <wielkiegie@gmail.com>
Reviewed-by: Bas Nieuwenhuizen <bas@basnieuwenhuizen.nl>