ix86: allow HLE store of accumulator to absolute address

ix86: allow HLE store of accumulator to absolute address

Since they're shorter to encode, the 0xa0...0xa3 encodings are preferred
for moves between accumulator and absolute address outside of 64-bit
mode. With HLE release semantics this encoding is unsupported though,
with the assembler raising an error. The operation is valid though, we
merely need to pick the longer encoding in that case.