fabrics: handle /dev/nvme-fabrics read failure

fabrics: handle /dev/nvme-fabrics read failure

The ability to read from /dev/nvme-fabrics to find supported options
is a newer Linux kernel feature added in f18ee3d988157 (5.17-rc1).
On earlier kernels, this read returns EINVAL,
preventing the controller from being added:
$ nvme discover --transport tcp --traddr 192.168.1.62
Failed to read from /dev/nvme-fabrics: Invalid argument
failed to add controller, error Invalid argument

So don't treat EINVAL as a fatal error, and instead fall back
to a default set of supported options.
With this change, controllers can be created successfully:
$ nvme discover --transport tcp --traddr 192.168.1.62

Discovery Log Number of Records 4, Generation counter 125
...

Fixes: d123131f2e ("fabrics: Do not pass unsupported options to kernel")
Signed-off-by: Caleb Sander <csander@purestorage.com>