dcache: Simplify logic in RELOAD_WAIT_ACK state

dcache: Simplify logic in RELOAD_WAIT_ACK state

Since the expression is_last_row(r1.store_row, r1.end_row_ix) can only
be true when stbs_done is true, there is no need to include stbs_done
in the expression for the reload being completed, and hence no need to
compute stbs_done in the RELOAD_WAIT_ACK state.

Signed-off-by: Paul Mackerras <paulus@ozlabs.org>