net: hns: Fix for variable may be used uninitialized warnings

When !CONFIG_REGMAP hns throws compiler warnings since
dsaf_read_syscon ignores the return result from regmap_read,
which allows val to be uninitialized.

Fixes: 86897c96 ("net: hns: add syscon operation for dsaf")
Reported-by: Jason Gunthorpe <jgg@ziepe.ca>
Signed-off-by: Huazhong Tan <tanhuazhong@huawei.com>
Signed-off-by: Yunsheng Lin <linyunsheng@huawei.com>
Signed-off-by: David S. Miller <davem@davemloft.net>