Fix clock size in carousel is wrong in foldable

The cause of this bug is that when we have splitshade in foldable, we
override screen_preview_width with
screen_preview_width_for_2_pane_small_width for wallpaper preview in
carousel but not for the clock part.

Test: manual
Bug: 283117384
Change-Id: I58cf1fb9ce9ca5d8a25ed520be9e80ba1f9ae94a