Sync with configure build: dct_neon.c and error_neon.c in
av1/encoder/arm/neon moved to the high bit depth build else.
They are only built when CONFIG_HIGHBITDEPTH is off.

Also moves both source files to AOM_AV1_COMMON_INTRIN_NEON
list since the configure build includes them in av1_{cx,dx}.mk.

Change-Id: Ie315e151438151f02a3aa5ef4757daf7d24f9028