scsi: target: core: Fix a pr_debug() argument

Print the string for which conversion failed instead of printing the
function name twice.

Fixes: 2650d71e ("target: move transport ID handling to the core")
Cc: Christoph Hellwig <hch@lst.de>
Link: https://lore.kernel.org/r/20191107215525.64415-1-bvanassche@acm.org


Signed-off-by: Bart Van Assche <bvanassche@acm.org>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>