[RISCV][NFC] Split InterleavedAccess related TLI hooks into a separate file (#148040)

There have been discussions on splitting RISCVISelLowering.cpp. I think
InterleavedAccess related TLI hooks would be some of the low hanging
fruit as it's relatively isolated and also because X86 is already doing
it.

NFC.

Author: mshockwave

llvm/lib/Target/RISCV/CMakeLists.txt

@@ -45,6 +45,7 @@ add_llvm_target(RISCVCodeGen
   RISCVInsertVSETVLI.cpp
   RISCVInsertWriteVXRM.cpp
   RISCVInstrInfo.cpp
+  RISCVInterleavedAccess.cpp
   RISCVISelDAGToDAG.cpp
   RISCVISelLowering.cpp
   RISCVLandingPadSetup.cpp