[clang][NFC] Rename SemaRISCVVectorLookup.cpp into SemaRISCV.cpp

In preparation for #92682.

Author: Endilll

clang/lib/Sema/CMakeLists.txt

@@ -60,7 +60,7 @@ add_clang_library(clangSema
   SemaOpenMP.cpp
   SemaOverload.cpp
   SemaPseudoObject.cpp
-  SemaRISCVVectorLookup.cpp
+  SemaRISCV.cpp
   SemaStmt.cpp
   SemaStmtAsm.cpp
   SemaStmtAttr.cpp