soc: ti: omap-prm: add am4 PRM data

Add PRM instance data for am4 family of SoCs. Initially this is just
used to provide reset support.

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>