Enable etnaviv for aarch64
The PKGBUILD enables etnaviv driver only for armv7:
case "${CARCH}" in
armv6h) GALLIUM=",vc4" ;;
armv7h) GALLIUM=",etnaviv,kmsro,lima,panfrost,tegra,vc4" ;;
aarch64) GALLIUM=",kmsro,lima,panfrost,v3d,vc4" ;;
There are several aarch64 platforms that contain Vivante GPUs supported by the etnaviv driver these days, including i.MX8M used by such devices as Librem 5 or MNT Reform.
Related: https://gitlab.manjaro.org/manjaro-arm/packages/extra/mesa-git/-/issues/2