[X86] Don't call LowerSETCC from LowerSELECT for STRICT_FSETCC/STRICT_FSETCCS nodes.

This causes the STRICT_FSETCC/STRICT_FSETCCS nodes to lowered
early while lowering SELECT, but the output chain doesn't get
connected. Then we visit the node again when it is its turn
because we haven't replaced the use of the chain result. In the
case of the fp128 libcall lowering, after D72341 this will cause
the libcall to be emitted twice.