Workaround fix for earlyexit of bottomup partition search (#876)
Workaround fix for earlyexit of bottomup partition search (#876)

Enable early-exit of bottomup partition search (i.e speed 0) for PARTITION_SPLIT only
and don't do early-exit with PARTITOIN_HORZ or PARTITION_VERT.
This will lead to no change in bdrate.

Most of the speed gain is preserved.
xiph/rav1e,xiph/rav1e