Encoder: Fixed unaligned access of i1_ref_idx and u1_mv in cabac context

i1_ref_idx and u1_mv in cabac context are defined as char,
but were typecasted to int and were accessed, and were not
aligned to 4 byte boundary.
This results in an undefined behaviour

Bug: 33073518
Test: Tested with -fsanitize=alignment enabled on avcenc
Change-Id: Ie4a73de076a9239f2d8707af68b7d2cd796aa803
1 file changed