Commit c073fda1c6 upstream changed the
return type for `plat_get_syscnt_freq()` from uint64_t to unsigned
long long.
This patch modifies the return type for the Tegra186 platform.
Change-Id: Ic9e5c364b90972265576e271582a4347e5eaa6eb
Signed-off-by: Varun Wadekar <vwadekar@nvidia.com>