Disable chroma_sub8x8 with chroma_2x2.

Resolves mismatch between CMake and configure build configs.

BUG=aomedia:856

Change-Id: I0ffbbec04a2a1b39d70f16e9509bd0cf7618ee88

build/cmake/aom_configure.cmake

@@ -164,6 +164,10 @@ if (CONFIG_VAR_TX_NO_TX_MODE AND NOT CONFIG_VAR_TX)
    change_config_and_warn(CONFIG_VAR_TX 1 CONFIG_VAR_TX_NO_TX_MODE)
 endif()
 
+if (CONFIG_CHROMA_2X2)
+  change_config_and_warn(CONFIG_CHROMA_SUB8X8 0 CONFIG_CHROMA_2X2)
+endif ()
+
 if (CONFIG_DAALA_TX)
    set(CONFIG_DAALA_DCT4 1)
    set(CONFIG_DAALA_DCT8 1)