Update revision of SPIR-V translator

Latest changes from master were backported to llvm_release_80 branch in the
translator repository by
KhronosGroup/SPIRV-LLVM-Translator#207
Picking up the updated translator.

Author: AlexeySotkin

CMakeLists.txt

@@ -84,7 +84,7 @@ if(NOT USE_PREBUILT_LLVM)
     set(CLANG_BASE_REVISION ccfe04576c13497b9c422ceef0b6efe99077a392)
 
     set(SPIRV_SOURCE_DIR ${LLVM_SOURCE_DIR}/projects/llvm-spirv)
-    set(SPIRV_BASE_REVISION 83298e3c9b124486c16d0fde54c764a6c5a2b554)
+    set(SPIRV_BASE_REVISION 6b3920fed310f223b1a69b0273eb7c243d9f6257)
 
     apply_patches(${CLANG_SOURCE_DIR}
                   ${CMAKE_CURRENT_SOURCE_DIR}/patches/clang