It is somewhat counterintuitive, but the correct flag for the memory
operand is "OSIZE". The "nw" flag takes care of promoting the default
operand size on 64 bits to 64.
Fixes: https://github.com/netwide-assembler/nasm/issues/130
Signed-off-by: H. Peter Anvin (Intel) <hpa@zytor.com>
