soc: ti: omap-prm: add data for am33xx

Add PRM instance data for AM33xx SoC. Includes some basic register
definitions and reset data for now.

Reviewed-by: Tony Lindgren <tony@atomide.com>
Signed-off-by: Tero Kristo <t-kristo@ti.com>
Signed-off-by: Santosh Shilimkar <santosh.shilimkar@oracle.com>