[SYCL] Add support for SYCL math functions
This PR adds support for SYCL math functions. Math functions in the std
namespace cannot be used inside SYCL kernels and those in the sycl
namespace should be used instead.
It follows the discussions in #1132 and the PR #1285 that introduced USM support for SYCL.
The macro EIGEN_USING_STD
has been split in EIGEN_USING_STD
for non-math functions and EIGEN_USING_STD_MATH
for math functions.
This change has effects only when EIGEN_USE_SYCL
is defined and allows to use math functions in the sycl
namespace.
When EIGEN_USE_SYCL
is NOT defined, nothing changes wrt before.
In some places using std::...
was used directly instead of EIGEN_USING_STD
. These as well have been replaced with EIGEN_USING_STD_MATH
.