qemu: Validate ARM CPU features
qemu: Validate ARM CPU features

This introduces semantic validation for SVE-related features,
preventing the user from combining them in invalid ways; it also
automatically enables overall SVE support if any SVE vector
length has been enabled by the user to make sure QEMU behaves
correctly.

Signed-off-by: Andrea Bolognani <3ada0bee826c753786fdbba72243dfba997094cf@redhat.com>
Tested-by: Andrew Jones <20ca6a98b2289e315ee985b8cb9cb36522e95d55@redhat.com>
Reviewed-by: Michal Privoznik <83d82aaba2eed257f4814b0c239c260c4caaadf0@redhat.com>

zippy2/libvirt,fabianfreyer/libvirt,crobinso/libvirt,jardasgit/libvirt,jfehlig/libvirt,jardasgit/libvirt,olafhering/libvirt,jardasgit/libvirt,fabianfreyer/libvirt,olafhering/libvirt,nertpinx/libvirt,zippy2/libvirt,crobinso/libvirt,jfehlig/libvirt,crobinso/libvirt,libvirt/libvirt,crobinso/libvirt,fabianfreyer/libvirt,nertpinx/libvirt,zippy2/libvirt,fabianfreyer/libvirt,jfehlig/libvirt,fabianfreyer/libvirt,libvirt/libvirt,nertpinx/libvirt,nertpinx/libvirt,jardasgit/libvirt,olafhering/libvirt,libvirt/libvirt,libvirt/libvirt,zippy2/libvirt,jardasgit/libvirt,nertpinx/libvirt,jfehlig/libvirt,olafhering/libvirt