Access ptimer_src_freq from gk20a instead of gk20a_platform. JIRA NVGPU-16 Change-Id: I3f2fcd22eb8a14c83ee2d481ff9f5acdf00f9c07 Signed-off-by: Terje Bergstrom <tbergstrom@nvidia.com> Reviewed-on: http://git-master/r/1463534 Reviewed-by: mobile promotions <svcmobile_promotions@nvidia.com> Tested-by: mobile promotions <svcmobile_promotions@nvidia.com>