staging: lustre: discard linux-time.h

Very little is left in linux-time.h.
Move CFS_TICK to libcfs.h discard the test.

Signed-off-by: NeilBrown <neilb@suse.com>
Reviewed-by: James Simmons <jsimmons@infradead.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>