Add proper description for error inject registers
Add proper description for error inject registers

Note: Only our latest-greatest experimental bitstreams support this
at this point in time. Later it will go into the new bitstreams.

ferseiti/genwqe-user,ferseiti/genwqe-user,ibm-genwqe/genwqe-user,tblume/genwqe-user,ibm-genwqe/genwqe-user,ibm-genwqe/genwqe-user,tblume/genwqe-user