configure.ac: move AC_ARG_ENABLE([gallium-llvm] hunk further up

With next commits we'll require --enable-gallium-llvm (en route to a
greater good later on) for RADV. The latter is required to ensure that
as otherwise we'll fail to build.

Cc: Dave Airlie <airlied@redhat.com>
Cc: "17.0" <mesa-stable@lists.freedesktop.org>
Signed-off-by: Emil Velikov <emil.velikov@collabora.com>
Reviewed-by: Tobias Droste <tdroste@gmx.de>
(cherry picked from commit 38abcdba8a59e88a91d598951323b977fb3fa1ad)
1 file changed