i965/miptree: Drop an if case from retile_as_linear

Drop an if statement whose predicate never evaluates to true. row_pitch
belongs to a surface with non-linear tiling. According to
isl_calc_tiled_min_row_pitch, the pitch is a multiple of the tile width.
By looking at isl_tiling_get_info, we see that non-linear tilings have
widths greater than or equal to 128B.

Cc: <mesa-stable@lists.freedesktop.org>
Reviewed-by: Chris Wilson <chris@chris-wilson.co.uk>

src/mesa/drivers/dri/i965/intel_mipmap_tree.c

@@ -519,10 +519,6 @@ need_to_retile_as_linear(struct brw_context *brw, unsigned row_pitch,
    if (tiling == ISL_TILING_LINEAR)
       return false;
 
-    /* If the width is much smaller than a tile, don't bother tiling. */
-   if (row_pitch < 64)
-      return true;
-
    if (ALIGN(row_pitch, 512) >= 32768) {
       perf_debug("row pitch %u too large to blit, falling back to untiled",
                  row_pitch);