[Coverity] Unnecessary copies in memory manager

[AlexeySachkov]

See issues at https://scan.coverity.com/projects/intel-llvm?tab=overview

CID 522848, 522863:

llvm/sycl/source/detail/memory_manager.cpp

Line 1066 in f9a7cc8

MemoryManager::fill_2d_usm(DstMem, Queue, Pitch, Width, Height,

CID 522853:

llvm/sycl/source/detail/memory_manager.cpp

Line 1101 in f9a7cc8

MemoryManager::copy_usm(Src, Queue, NumBytes,

CID `522858:

llvm/sycl/source/detail/memory_manager.cpp

Lines 1226 to 1230 in f9a7cc8

	if (IsDeviceImageScoped)
	memcpyToDeviceGlobalDirect(Queue, DGEntry, NumBytes, Offset, SrcMem,
	DepEvents, OutEvent);
	else
	memcpyToDeviceGlobalUSM(Queue, DGEntry, NumBytes, Offset, SrcMem, DepEvents,

CID 522860:

llvm/sycl/source/detail/memory_manager.cpp

Lines 1248 to 1253 in f9a7cc8

	if (IsDeviceImageScoped)
	memcpyFromDeviceGlobalDirect(Queue, DGEntry, NumBytes, Offset, DstMem,
	DepEvents, OutEvent);
	else
	memcpyFromDeviceGlobalUSM(Queue, DGEntry, NumBytes, Offset, DstMem,
	DepEvents, OutEvent);

CID 522862:

llvm/sycl/source/detail/memory_manager.cpp

Line 1137 in f9a7cc8

MemoryManager::copy_usm(reinterpret_cast<const char *>(Src) + Offset, Queue,