broadcom/vc5: Add appropriate height padding for bank conflicts.

broadcom/vc5: Add appropriate height padding for bank conflicts.

I thought I didn't need this because I was doing level-0-always-UIF and
that the pad there would propagate down, but it turns out that for level 1
the padding ends up being chosen by the HW.  This brings us closer to
being able to turn on UIF XOR for increased performance, as well.