fpga: stratix10-soc: Do not use ret uninitialized in s10_probe()

Clang warns:

drivers/fpga/stratix10-soc.c:431:9: warning: variable 'ret' is uninitialized when used here [-Wuninitialized]
return ret;
^~~

ret is only assigned in an error path now so just return 0 directly.

Fixes: 4ba0b2c294fe ("fpga: mgr: Use standard dev_release for class driver")
Link: https://github.com/ClangBuiltLinux/linux/issues/1517
Reviewed-by: Russ Weight <[e-mail]>
Reviewed-by: Tom Rix <[e-mail]>
Acked-by: Xu Yilun <[e-mail]>
Signed-off-by: Nathan Chancellor <[e-mail]>
Signed-off-by: Moritz Fischer <[e-mail]>

drivers/fpga/stratix10-soc.c

···
 	}
 
 	platform_set_drvdata(pdev, mgr);
-	return ret;
+	return 0;
 
 probe_err:
 	stratix10_svc_free_channel(priv->chan);