ARM: OMAP4: prm: fix interrupt register offsets

Previous code used wrong instance for the interrupt register access.
Use the right one which is OCP_SOCKET.

Signed-off-by: Tero Kristo <t-kristo@ti.com>
Cc: Paul Walmsley <paul@pwsan.com>
Reviewed-by: Santosh Shilimkar <santosh.shilimkar@ti.com>
Signed-off-by: Paul Walmsley <paul@pwsan.com>