[GVN] Don't short-circuit load PRE

[GVN] Don't short-circuit load PRE

4ad41902e8c7481ccf3cdf6e618dfcd1e1fc10fc changed this code to
propagate Changed if scalar GEP PRE is performed. However, as
implemented this would skip the load PRE entirely if GEP indices
were PREd. Make sure load PRE runs even if Changed is already
true.

This likely has no functional effect as load PRE would then
occur on a later GVN iteration.