Revert BufferObject's size to size_t like before 45a0ceecfbe4

shared/source/os_interface/linux/drm_memory_manager.cpp:61:54: error: non-const
      lvalue reference to type 'size_t' (aka 'unsigned int') cannot bind to a value of unrelated type 'uint64_t'
      (aka 'unsigned long long')
                    bo->gpuAddress = acquireGpuRange(bo->size, false, rootDeviceIndex, false);
                                                     ^~~~~~~~
shared/source/os_interface/linux/drm_memory_manager.h:66:38: note: passing argument
      to parameter 'size' here
    uint64_t acquireGpuRange(size_t &size, bool requireSpecificBitness, uint32_t rootDeviceIndex, bool requi...
                                     ^

SSE2 is not enabled by default on BSDs

core/utilities/clflush.cpp:16:5: error: '_mm_clflush' needs target feature sse2
    _mm_clflush(ptr);
    ^

--- shared/source/os_interface/linux/drm_buffer_object.h.orig	2020-05-21 10:39:12 UTC
+++ shared/source/os_interface/linux/drm_buffer_object.h
@@ -55,7 +55,7 @@ class BufferObject {
     std::atomic<uint32_t> refCount;
 
     int handle; // i915 gem object handle
-    uint64_t size;
+    size_t size;
     bool isReused;
 
     //Tiling
--- shared/source/utilities/cpuintrinsics.cpp.orig	2020-02-28 16:16:42 UTC
+++ shared/source/utilities/cpuintrinsics.cpp
@@ -12,6 +12,9 @@
 namespace NEO {
 namespace CpuIntrinsics {
 
+#ifdef __GNUC__
+__attribute__((target("sse2")))
+#endif
 void clFlush(void const *ptr) {
     _mm_clflush(ptr);
 }