[SYCL-MLIR] Revert [SYCL] Switch SPIR-V offload target to opaque pointers

Signed-off-by: Tsang, Whitney <whitney.tsang@intel.com>

Author: whitneywhtsang

llvm/CMakeLists.txt

@@ -893,7 +893,7 @@ set(DPCPP_ENABLE_OPAQUE_POINTERS FALSE CACHE BOOL
 if (DPCPP_ENABLE_OPAQUE_POINTERS)
   add_definitions("-DENABLE_OPAQUE_POINTERS=1")
 endif(DPCPP_ENABLE_OPAQUE_POINTERS)
-set(SPIRV_ENABLE_OPAQUE_POINTERS TRUE CACHE BOOL
+set(SPIRV_ENABLE_OPAQUE_POINTERS FALSE CACHE BOOL
     "Enable opaque pointers for SPIR-V offload by default.")
 if(SPIRV_ENABLE_OPAQUE_POINTERS)
   add_definitions("-DSPIRV_ENABLE_OPAQUE_POINTERS=1")