meson: add missing HAVE_RADEON

Signed-off-by: Eric Engestrom <eric.engestrom@imgtec.com>
Reviewed-by: Emil Velikov <emil.velikov@collabora.com>
Reviewed-by: Dylan Baker <dylan@pnwbakers.com>

meson.build

@@ -255,7 +255,7 @@ foreach t : [[with_intel, 'INTEL'], [with_vmwgfx, 'VMWGFX'],
              [with_nouveau, 'NOUVEAU'], [with_omap, 'OMAP'],
              [with_exynos, 'EXYNOS'], [with_freedreno, 'FREEDRENO'],
              [with_tegra, 'TEGRA'], [with_vc4, 'VC4'],
-             [with_etnaviv, 'ETNAVIV']]
+             [with_etnaviv, 'ETNAVIV'], [with_radeon, 'RADEON']]
   if t[0]
     config.set10('HAVE_@0@'.format(t[1]), true)
   endif