USE_TXTYPE_SEARCH_FOR_SUB8X8_IN_CB4X4 macro added to turn
tx_type search on/off for sub8x8 in cb4x4 mode.

The purpose is mainly to analyze the coding gains from cb4x4
but this later can be made into a speed feature as well.

Change-Id: Ic22026c373eebba87f324689ac5686a2844315b6