target: fix deprecated attribute names in dmesg

The following message is displayed in dmesg when a deprecated attribute
is set:

  "ignoring deprecated ##_name## attribute"

This patch fixes the format to include the name of the deprecated
attribute.

Signed-off-by: Christophe Vu-Brugier <cvubrugier@fastmail.fm>
Reviewed-by: Sagi Grimberg <sagig@mellanox.com>
Signed-off-by: Nicholas Bellinger <nab@linux-iscsi.org>