ANDROID: GKI: time: Export for nsec_to_clock_t

    - Add EXPORT_SYMBOL_GPL for nsec_to_clock_t() so that drivers
    be loadable as a module.

    - This API is required by loadable driver module from samsung to
    fetch process uptime based on CPU clock ticks to get the exact time
    during which app is scheduled in user mode.
Signed-off-by: Abhilasha Rao <abhilasha.hv@samsung.corp-partner.google.com>
Bug: 158067689
Change-Id: I45be5fd7873dc7c21aa583313499f48f8b10bb1b