Revert "[SYCL] Check if the underlying buffer type is device copyable (#4914)"

Since sycl::vec is not a trivially copyable class, even though we
have defined a specialization for sycl::is_device_copyable template
for the sycl::vec class itself, it doesn't make any classes that have
members of the sycl::vec type device copyable since those classes aren't
trivially copyable yet. For example, a class from SYCL-CTS:

template <typename T>
struct image_accessor_failure_item {
  bool triggered;
  T value;
  T expected;

  image_accessor_failure_item() :
    triggered(false),
    value(0),
    expected(0) {}
};

is not trivially copyable since it has two fields: value and expected of
type sycl::vec; therefore, the class is not device copyable and a
compilation error occurs when a sycl::buffer is created for this class
instances.

The regression makes us to revert the commit and delay adding the check
until the sycl::vec class is modified to be trivially copyable.

This reverts commit 61f1ae6.

Author: Pavel Samolysov

sycl/include/CL/sycl/buffer.hpp

@@ -14,7 +14,6 @@
 #include <CL/sycl/exception.hpp>
 #include <CL/sycl/property_list.hpp>
 #include <CL/sycl/stl.hpp>
-#include <CL/sycl/types.hpp>
 #include <sycl/ext/oneapi/accessor_property_list.hpp>
 
 __SYCL_INLINE_NAMESPACE(cl) {
@@ -45,10 +44,6 @@ template <typename T, int dimensions = 1,
           typename __Enabled = typename detail::enable_if_t<(dimensions > 0) &&
                                                             (dimensions <= 3)>>
 class buffer {
-  static_assert(
-      is_device_copyable<T>::value,
-      "The underlying data type of a buffer 'T' must be device copyable");
-
 public:
   using value_type = T;
   using reference = value_type &;

sycl/include/CL/sycl/types.hpp

@@ -2420,13 +2420,6 @@ struct is_device_copyable<sycl::marray<T, N>,
                           std::enable_if_t<is_device_copyable<T>::value>>
     : std::true_type {};
 
-// vec is device copyable on host, on device vec is trivially copyable
-// and therefore is device copyable too.
-#ifndef __SYCL_DEVICE_ONLY__
-template <typename T, int N>
-struct is_device_copyable<sycl::vec<T, N>> : std::true_type {};
-#endif
-
 namespace detail {
 template <typename T, typename = void>
 struct IsDeprecatedDeviceCopyable : std::false_type {};