MFC r314998: Fix FC target mode in mpt(4), broken in multiple ways.

MFC r314998: Fix FC target mode in mpt(4), broken in multiple ways.

 - Not set BufferLength caused receive of empty ATIOs.
 - CDB length guessing was broken at least for RC16.
 - mpt_req_untimeout() was called with wrong req parameter.
 - Sense data reporting was broken in several ways.

With this change my LSI7204EP-LC can pass at least basic tests as target.
The code is still far from perfect, but finally I found second hw/driver
after isp(4) that really can work in CAM target mode.

git-svn-id: svn://svn.freebsd.org/base/stable/10@315821 ccf9f872-aa2e-dd11-9fc8-001c23d0bc1f