ARM: OMAP2+: AM43x: early init

Minimal early init - PRCM initialization not yet taken care.

Control module is similar (base address, feature register etc.) as
that of AM335x, while PRCM base address is different. Instead of
adding a new header file for AM43x, PRCM base address is added in
AM335x header file as it is similar to it to a large extent.

Signed-off-by: Afzal Mohammed <afzal@ti.com>
[tony@atomide.com: updated to drop am33xx_check_features()]
Signed-off-by: Tony Lindgren <tony@atomide.com>