24xx clock: associate clocks with clockdomains

Associate each OMAP24xx clock in arch/arm/mach-omap2/clock24xx.h
with a clockdomain.

Also move the L4 clock up higher in the file in preparation to
define the SSI L4 iclk.
Signed-off-by: Paul Walmsley <paul@pwsan.com>
Signed-off-by: Tony Lindgren <tony@atomide.com>