bus: omap-ocp2scp: Fix error handling in omap_ocp2scp_probe

The error handling code in omap_ocp2scp_probe fails to invoke
pm_runtime_disable and fails to initialize return value in
certain cases. Fix it here.

Signed-off-by: Kishon Vijay Abraham I <kishon@ti.com>
Signed-off-by: Sekhar Nori <nsekhar@ti.com>
Signed-off-by: Tony Lindgren <tony@atomide.com>