arm64: mc: NEON implementation of blend, blend_h and blend_v function

                   	A73	A53
blend_h_w2_8bpc_c:	184.7	301.5
blend_h_w2_8bpc_neon:	58.8	104.1
blend_h_w4_8bpc_c:	291.4	507.3
blend_h_w4_8bpc_neon:	48.7	108.9
blend_h_w8_8bpc_c:	510.1	992.7
blend_h_w8_8bpc_neon:	66.5	99.3
blend_h_w16_8bpc_c:	972	1835.3
blend_h_w16_8bpc_neon:	82.7	145.2
blend_h_w32_8bpc_c:	776.7	912.9
blend_h_w32_8bpc_neon:	155.1	266.9
blend_h_w64_8bpc_c:	1424.3	1635.4
blend_h_w64_8bpc_neon:	273.4	480.9
blend_h_w128_8bpc_c:	3318.1	3774
blend_h_w128_8bpc_neon:	614.1	1097.9
blend_v_w2_8bpc_c:	278.8	427.5
blend_v_w2_8bpc_neon:	113.7	170.4
blend_v_w4_8bpc_c:	960.2	1597.7
blend_v_w4_8bpc_neon:	222.9	351.4
blend_v_w8_8bpc_c:	1694.2	3333.5
blend_v_w8_8bpc_neon:	200.9	333.6
blend_v_w16_8bpc_c:	3115.2	5971.6
blend_v_w16_8bpc_neon:	233.2	494.8
blend_v_w32_8bpc_c:	3949.7	6070.6
blend_v_w32_8bpc_neon:	460.4	841.6
blend_w4_8bpc_c:	244.2	388.3
blend_w4_8bpc_neon:	25.5	66.7
blend_w8_8bpc_c:	616.3	1120.8
blend_w8_8bpc_neon:	46	110.7
blend_w16_8bpc_c:	2193.1	4056.4
blend_w16_8bpc_neon:	140.7	299.3
blend_w32_8bpc_c:	2502.8	2998.5
blend_w32_8bpc_neon:	381.4	725.3