IB/hfi1: Fix error return code in parse_platform_config()

Fix to return a negative error code from the error handling case instead
of 0, as done elsewhere in this function.

Fixes: 77241056

 ("IB/hfi1: add driver files")
Link: https://lore.kernel.org/r/20210408113140.103032-1-wangwensheng4@huawei.com
Reported-by: Hulk Robot <hulkci@huawei.com>
Signed-off-by: Wang Wensheng <wangwensheng4@huawei.com>
Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>