nvmet: use type-name map for address treq

Currently nvmet_addr_treq_[store|show]() uses switch and if else
ladder for address transport requirements to string and reverse
mapping. With addtion of the generic nvmet_type_name_map structure
we can get rid of the switch and if else ladder with string
duplication.

Signed-off-by: Chaitanya Kulkarni <chaitanya.kulkarni@wdc.com>
Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Jens Axboe <axboe@kernel.dk>