switch default cmake script to dyndisp. (#552)

Author: xuhancn

CMakeLists.txt

@@ -46,11 +46,4 @@ set(DPCPP_THIRD_PARTY_ROOT "${PROJECT_SOURCE_DIR}/third_party")
 list(APPEND CMAKE_MODULE_PATH ${PROJECT_SOURCE_DIR}/cmake/Modules)
 
 # Common dependencies
-
-# The DYN_DISP is a temporary flag, and it should be switch to dynamic dispatch after 
-# we fully support dynamic dispatch runtime.
-if("$ENV{DYN_DISP}" STREQUAL "1")
-include(cmake/CpuDynDisp.cmake)
-else()
-include(cmake/CPU.cmake)
-endif()
+include(cmake/CpuDynDisp.cmake)