BNDMK, BNDLDX, and BNDSTX are split-SIB (MIB) instructions, but do
*not* require a SIB encoding. However, TILELOAD* and TILESTORE* *do*
require a SIB in all cases. Split the MIB flag into MIB (split
address) and SIB (SIB required) flags.
This fixes travis test mpx.
Signed-off-by: H. Peter Anvin (Intel) <hpa@zytor.com>