Remove unused macro to fix the following compilation warning:

drivers/target//target_core_pscsi.c:37: warning: macro "ISPRINT" is not used [-Wunused-macros]
	#define ISPRINT(a)  ((a >= ' ') && (a <= '~'))

Link: https://lore.kernel.org/r/20210228055645.22253-7-chaitanya.kulkarni@wdc.comReviewed-by: Mike Christie <michael.christie@oracle.com>
Reviewed-by: Johannes Thumshirn <johannes.thumshirn@wdc.com>
Signed-off-by: Chaitanya Kulkarni <chaitanya.kulkarni@wdc.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>