ANDROID: GKI: loadavg: Export for get_avenrun

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

    - This API is required by loadable driver module
    to get Number of jobs in the run queue  (state R) or waiting
    for disk I/O(state D) averaged over 1 min.

Signed-off-by: Abhilasha Rao <abhilasha.hv@samsung.corp-partner.google.com>
Signed-off-by: Todd Kjos <tkjos@google.com>
Bug: 158067689
Change-Id: I56c12c908be068f78e16004df876be3bee0e7229