[mlir][spirv] NFC: rename SPIR-V conversion files for consistency

This commit renames various SPIR-V related conversion files for
consistency. It drops the "Convert" prefix to various files and
fixes various comment headers.

Reviewed By: hanchung, ThomasRaoux

Differential Revision: https://reviews.llvm.org/D93489
diff --git a/mlir/lib/Conversion/LinalgToSPIRV/LinalgToSPIRV.cpp b/mlir/lib/Conversion/LinalgToSPIRV/LinalgToSPIRV.cpp
index 0e09d95..8133a37 100644
--- a/mlir/lib/Conversion/LinalgToSPIRV/LinalgToSPIRV.cpp
+++ b/mlir/lib/Conversion/LinalgToSPIRV/LinalgToSPIRV.cpp
@@ -1,4 +1,4 @@
-//===- LinalgToSPIRV.cpp - Linalg to SPIR-V dialect conversion ------------===//
+//===- LinalgToSPIRV.cpp - Linalg to SPIR-V Patterns ----------------------===//
 //
 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
 // See https://llvm.org/LICENSE.txt for license information.