staging/lustre/libcfs: Move private tracefile structs out of header

the struct page_collection, struct cfs_trace_page and
struct tracefiled_ctl are only used by tracefile.c, so move them
there.

Signed-off-by: Oleg Drokin <green@linuxhacker.ru>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>