Fix a bug in Graphics Allocations constructors.

- There was a wrong cast in Graphics Allocation constructor resulting
in wrong GPU address generation in some sporadic scenarios.
- Problem appears in 32 bit applications where void* address is cast to
uint64_t value, if c style cast is used it makes trailing bit to be
populated to higher bits constructing wrong value

0xf000000 is being casted to 0xfffffffff0000000 while it should be casted to
0x00000000f0000000
- added special cast function for further use.

Change-Id: I56d53a8e13e17cbacd127566442eea3f6a089977

unit_tests/helpers/ptr_math_tests.cpp

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2017, Intel Corporation
+ * Copyright (c) 2017 - 2018, Intel Corporation
  *
  * Permission is hereby granted, free of charge, to any person obtaining a
  * copy of this software and associated documentation files (the "Software"),
@@ -51,3 +51,11 @@ TEST(PtrMath, addrToPtr) {
     EXPECT_EQ(ptr32BitAddr, addrToPtr(addr32Bit));
     EXPECT_EQ(ptr64BitAddr, addrToPtr(addr64Bit));
 }
+
+TEST(PtrMath, givenCastToUint64FunctionWhenItIsCalledThenProperValueIsReturned) {
+    uintptr_t address = 0xf0000000;
+    void *addressWithTrailingBitSet = reinterpret_cast<void *>(address);
+    uint64_t expectedUint64Address = 0xf0000000;
+    auto uintAddress = castToUint64(addressWithTrailingBitSet);
+    EXPECT_EQ(uintAddress, expectedUint64Address);
+}