This patch changes bcu.c to calculate clock at any time.  Because clock can
be changed.  Moreover, EXPORT_SYMBOL_GPLs are added to it.
Signed-off-by: Yoichi Yuasa <yuasa@hh.iij4u.or.jp>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>