i965/fs: Fix fs_inst::regs_read() for sources in the ATTR file.
Otherwise it would crash on Gen8 with scalar VS. The issue can easily be reproduced with the following patch, but I don't see any reason why it wouldn't be possible to end up with an ATTR argument here even without it. CC: mesa-stable@lists.freedesktop.org Reviewed-by:Connor Abbott <connor.w.abbott@intel.com> Reviewed-by:
Jason Ekstrand <jason@jlekstrand.net>