Seperate prediction mode and tx type search for inter
modes. Enabled for speed >=1.

baseline:
speed increase     40%
compression drop   0.30%/0.29% on lowres/midres

ext-tx:
speed increase    160%
compression drop  1.08%/0.95% on lowres/midres

Change-Id: Ieb34b1ee80df6980d16e26a5783e08cc0deae55b