Add cl_khr_subgroups pragma enable in the kernel source (#609)
Add cl_khr_subgroups pragma enable in the kernel source (#609)

code for test_api sub_group_dispatch. Although subgroups
is a core feature there is no separate 2.1 language spec
so we use the 2.0 with the pragma.

Signed-off-by: John Kesapides <6082e42ffcc7c726f5d54ff530aa4e23cb527c43@arm.com>
KhronosGroup/OpenCL-CTS,KhronosGroup/OpenCL-CTS,KhronosGroup/OpenCL-CTS,KhronosGroup/OpenCL-CTS