drm/amdkfd: Set gws_mask to 64 bit 1s

Previous kfd doesn't use gws so this mask was set to 0.
Set it to 64 bit 1s because now kfd can use all 64 gws
resources.

Signed-off-by: Oak Zeng <Oak.Zeng@amd.com>
Reviewed-by: Felix Kuehling <Felix.Kuehling@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>