Update mpr(4) driver from v15 to v18 from Broadcom site.
Version 16 is just a number bump, since we already had those changes.
Version 17 introduces new AdapterType value, that allows new user-space
tools from Broadcom to differentiate adapter generations 3 and 3.5.
Version 18 updates headers and adds SAS_DEVICE_DISCOVERY_ERROR reporting.
MFC after: 2 weeks