Reuse OMAP4 operations on AM43x.

Context related ops are not used on AM43x, as this would not add value
when using DT and AM43x is DT only boot. This additionally helps not to
add context register offset for each hwmod.
Signed-off-by: NAmbresh K <ambresh@ti.com>
Signed-off-by: NAfzal Mohammed <afzal@ti.com>
Acked-by: NRajendra Nayak <rnayak@ti.com>
Acked-by: NTony Lindgren <tony@atomide.com>
Signed-off-by: NPaul Walmsley <paul@pwsan.com>