armv8: Fix ime_calculate_sad3_prog_av8

Previously, this used x5 (which is a stride parameter)
as destination pointer, and overwrote the destination in x6
with a counter, and looped to a label in another function.

In practice, this function is never used, which is why this
hasn't been noticed before.

Change-Id: Iab87a2960c36b7dc4de4216b1d4bbbe4e9f03578
1 file changed