If the start bit, PxCMD.ST, is cleared and nothing is in-flight then
PxCI, PxSACT, PxCMD.CCS and PxCMD.CR should be 0.

Reviewed by:	grehan


git-svn-id: svn+ssh://svn.freebsd.org/base/head@274045 ccf9f872-aa2e-dd11-9fc8-001c23d0bc1f