gallium/os: fix os_time_get_nano() to roll over less
Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=102241 Cc: mesa-stable@lists.freedesktop.org Reviewed-by:Brian Paul <brianp@vmware.com> Reviewed-by:
Jose Fonseca <jfonseca@vmware.com> (cherry picked from commit 7fb7287c)