nvmet-tcp: remove redundant calls to nvmet_tcp_fatal_error()

nvmet-tcp: remove redundant calls to nvmet_tcp_fatal_error()

Executing nvmet_tcp_fatal_error() is generally the responsibility
of the caller (nvmet_tcp_try_recv); all other functions should
just return the error code.

Remove the nvmet_tcp_fatal_error() function, it's not needed
anymore.

Reviewed-by: Hannes Reinecke <hare@suse.de>
Reviewed-by: Chaitanya Kulkarni <kch@nvidia.com>
Signed-off-by: Maurizio Lombardi <mlombard@redhat.com>
Signed-off-by: Keith Busch <kbusch@kernel.org>