nvme: parse reservation commands's action and rtype to string

Parse reservation commands's action(including rrega, racqa and rrela)
and rtype to string to make the trace log more human-readable.

Signed-off-by: Guixin Liu <kanie@linux.alibaba.com>
Reviewed-by: Sagi Grimberg <sagi@grimberg.me>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Chaitanya Kulkarni <kch@nvidia.com>
Signed-off-by: Keith Busch <kbusch@kernel.org>