[LegalizeDAG] Modify ExpandLegalINT_TO_FP to swap data for little/big endian...

[LegalizeDAG] Modify ExpandLegalINT_TO_FP to swap data for little/big endian instead of the pointers.

Will make it easier to pass the pointer info and alignment
correctly to the loads/stores.

While there also make the i32 stores independent and use a token
factor to join before the load.