IB/srp: replace custom implementation of hex2bin()

There is no need to have a duplication of the generic library, i.e.
hex2bin().

Replace the open coded variant.
Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Acked-by: Bart Van Assche <bart.vanassche@wdc.com>
Signed-off-by: Jason Gunthorpe <jgg@mellanox.com>

drivers/infiniband/ulp/srp/ib_srp.c

@@ -3110,7 +3110,6 @@ static int srp_parse_options(const char *buf, struct srp_target_port *target)
 {
 	char *options, *sep_opt;
 	char *p;
-	char dgid[3];
 	substring_t args[MAX_OPT_ARGS];
 	int opt_mask = 0;
 	int token;
@@ -3162,16 +3161,10 @@ static int srp_parse_options(const char *buf, struct srp_target_port *target)
 				goto out;
 			}
 
-			for (i = 0; i < 16; ++i) {
-				strlcpy(dgid, p + i * 2, sizeof(dgid));
-				if (sscanf(dgid, "%hhx",
-					   &target->orig_dgid.raw[i]) < 1) {
-					ret = -EINVAL;
+			ret = hex2bin(target->orig_dgid.raw, p, 16);
 			kfree(p);
+			if (ret < 0)
 				goto out;
-				}
-			}
-			kfree(p);
 			break;
 
 		case SRP_OPT_PKEY: