Initialize best_tx_size with invalid value

If vp9_pick_inter_mode works properly, it should at least check
one coding mode and hence get best_tx_size assigned a valid value.
There is no need to initialize best_tx_size with a legitimate
value before starting the mode search.

Change-Id: Ic0496cd89672ea9c2c512a9bd1da952190af9cba
Merge "Initialize best_tx_size with invalid value"
Fixed MFQE crash issue for highbit depth.

Check the flags, no MFQE for highbit now. Will add highbit support
latter.

Change-Id: I548c27593e0f47ab7f4c92b45f14fb037dc86591
Merge "Fixed MFQE crash issue for highbit depth."
VP9 common for ARMv8 by using NEON intrinsics 19

Delete vp9_dc_only_idct_add_neon.c

The function was merged with vp9_short_idct4x4_1_add (later
vp9_idct4x4_1_add) in d2de1ca and should have been deleted then.

Change-Id: Ie58ba3dd9dc7330a8f1238dd7dd71c9ed4639b94
Signed-off-by: James Yu <james.yu@linaro.org>