MFC r272936:
Update isp_tgt_map and send new arrival notification if target that departed
earlier has returned.  Previously that code worked only once, confusing CTL.
MFC r274253: Fix LUN resize broken by r272911 commit.
MFC r274080: Improve error handling around duplicate lun and port enable.

This fixes kernel panic if port enabled twice and then disabled.
MFC r274081: Fix residual copy/paste in r274080.