OMAP2/3 clock: every clock must have a clkdm

OMAP2/3 clock: every clock must have a clkdm

Every OMAP2/3 clock must now have an assigned clockdomain, so we can
remove the checks from clk_enable()/clk_disable().  Instead, verify
that the clockdomain is present only at clock init time via the
arch_clock clk_register() hook.

Signed-off-by: Paul Walmsley <paul@pwsan.com>
Signed-off-by: Tony Lindgren <tony@atomide.com>