i965/skl: Fix aligning mt->total_width to the block size

i965/skl: Fix aligning mt->total_width to the block size

brw_miptree_layout_2d tries to ensure that mt->total_width is a
multiple of the compressed block size, presumably because it wouldn't
be possible to make an image that has a fraction of a block. However
it was doing this by aligning mt->total_width to align_w. Previously
align_w has been used as a shortcut for getting the block width
because before Gen9 the block width was always equal to the alignment.
Commit 4ab8d59a2 tried to fix these cases to use the block width
instead of the alignment but it missed this case.

I think in practice this probably won't make any difference because
the buffer for the texture will be allocated to be large enough to
contain the entire pitch and libdrm aligns the pitch to the tile width
anyway. However I think the patch is worth having to make the
intention clearer.

Reviewed-by: Anuj Phogat <anuj.phogat@gmail.com>
Reviewed-by: Ben Widawsky <ben@bwidawsk.net>