The functions generic_encode() and generic_decode() code the lsb values
 as raw bits using the od_ec_enc_bits() and od_ec_dec_bits() functions.
These code bits in the reverse order as the aom_write_literal() and
 aom_read_literal() functions, so both the encoder and decoder must
 be changed at the same time.
This commit has no impact on metrics but is a bitstream change.

Change-Id: I83546e2d4b73c28a7f269ddc850742df53d227ce