ARM: AM33xx: fix module_wait_ready without clkctrl register

If the module has no clkctrl register defined, module_wait_ready should
not try to access this. This can potentially cause an illegal register
access, and result in bad idle reporting also.

Signed-off-by: Tero Kristo <t-kristo@ti.com>
Signed-off-by: Tony Lindgren <tony@atomide.com>