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: 4ba0b2c2 ("fpga: mgr: Use standard dev_release for class driver")
Link: https://github.com/ClangBuiltLinux/linux/issues/1517


Reviewed-by: Russ Weight <russell.h.weight@intel.com>
Reviewed-by: Tom Rix <trix@redhat.com>
Acked-by: Xu Yilun <yilun.xu@intel.com>
Signed-off-by: Nathan Chancellor <nathan@kernel.org>
Signed-off-by: Moritz Fischer <mdf@kernel.org>