til_fb: prevent 0-height slices

til_fb_fragment_slice_single() and indirectly
til_fragmenter_slice_per_cpu() could get into infinite loops when
slicing small fragments into many slices.

This became more likely with commit a2f7397 which increased
per_cpu slice counts by 16X, which is how I tripped over it
running rtv.  A checkers,size=8,fill_module=moire sent things
spinning...

This commit prevents it in the obvious manner.

0 files changed, 0 insertions, 0 deletions