add core.c, clock.c, and clock.h in mach-bcmring

implement timer init, clocksource init, amba device init
implement clock set/get enable/disable API
add dummy clkdev.h
Signed-off-by: NLeo Chen <leochen@broadcom.com>
Signed-off-by: NRussell King <rmk+kernel@arm.linux.org.uk>