arm64: itx: Fix the eob checking for dct_dct_64x16
arm64: itx: Fix the eob checking for dct_dct_64x16

Before this, we never did the early exit from the first pass.

Before:                               Cortex A53      A72      A73
inv_txfm_add_64x16_dct_dct_1_8bpc_neon:   7275.7   5198.3   5250.9
inv_txfm_add_64x16_dct_dct_2_8bpc_neon:   7276.1   5197.0   5251.3
inv_txfm_add_64x16_dct_dct_3_8bpc_neon:   7275.8   5196.2   5254.5
inv_txfm_add_64x16_dct_dct_4_8bpc_neon:   7273.6   5198.8   5254.2
After:
inv_txfm_add_64x16_dct_dct_1_8bpc_neon:   5187.8   3763.8   3735.0
inv_txfm_add_64x16_dct_dct_2_8bpc_neon:   7280.6   5185.6   5256.3
inv_txfm_add_64x16_dct_dct_3_8bpc_neon:   7270.7   5179.8   5250.3
inv_txfm_add_64x16_dct_dct_4_8bpc_neon:   7271.7   5212.4   5256.4

The other related variants didn't have this bug and properly exited
early when possible.

videolan/dav1d