ANDROID: GKI: cputime: Export for thread_group_cputime_adjusted

    - Add EXPORT_SYMBOL_GPL for thread_group_cputime_adjusted()
    to allow drivers to 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 duration of time app is scheduled in user mode.

Signed-off-by: Abhilasha Rao <abhilasha.hv@samsung.corp-partner.google.com>
Bug: 158067689
Change-Id: I1843de08edf5bb2eee806845f4b5e0a305da5fe7
(cherry picked from commit bf679b941237ae76d0bba8d98e670819e029847a)