spmi: Return meaningful errors in spmi_controller_alloc()

spmi_controller_alloc() currently returns NULL to all types of errors,
which can be improved.

Use appropriate error code in returns and pass the errors from used
functions where possible.

Signed-off-by: Fei Shao <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Stephen Boyd <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Greg Kroah-Hartman <[e-mail]>

drivers/spmi/spmi-devres.c

···
 		return ERR_PTR(-ENOMEM);
 
 	ctrl = spmi_controller_alloc(parent, size);
-	if (!ctrl) {
+	if (IS_ERR(ctrl)) {
 		devres_free(ptr);
-		return ERR_PTR(-ENOMEM);
+		return ctrl;
 	}
 
 	*ptr = ctrl;

drivers/spmi/spmi.c

···
 	int id;
 
 	if (WARN_ON(!parent))
-		return NULL;
+		return ERR_PTR(-EINVAL);
 
 	ctrl = kzalloc(sizeof(*ctrl) + size, GFP_KERNEL);
 	if (!ctrl)
-		return NULL;
+		return ERR_PTR(-ENOMEM);
 
 	device_initialize(&ctrl->dev);
 	ctrl->dev.type = &spmi_ctrl_type;
···
 		dev_err(parent,
 			"unable to allocate SPMI controller identifier.\n");
 		spmi_controller_put(ctrl);
-		return NULL;
+		return ERR_PTR(id);
 	}
 
 	ctrl->nr = id;