vp9: Clamp tx_size in model_rd_large

For nonrd_pickmode: add clamp/check to make
sure tx_size is not set to lower than 8X8,
for the model_rd_large function (which is only
called for big block sizes).

No change in behavior.

Change-Id: I9c6093068e406ac16cfd6784ba75868906225378
1 file changed