anv: Drop unused local variable

Leftover from 021fa28163 ("xintel/nir: Add a helper for getting
BRW_AOP from an intrinsic").

Acked-by: Eric Engestrom <eric.engestrom@intel.com>
Reviewed-by: Jason Ekstrand <jason@jlekstrand.net>

src/intel/compiler/brw_fs_nir.cpp

@@ -3963,7 +3963,6 @@ fs_visitor::nir_emit_intrinsic(const fs_builder &bld, nir_intrinsic_instr *instr
 
       /* Get some metadata from the image intrinsic. */
       const nir_intrinsic_info *info = &nir_intrinsic_infos[instr->intrinsic];
-      const GLenum format = nir_intrinsic_format(instr);
 
       fs_reg srcs[SURFACE_LOGICAL_NUM_SRCS];