usb: storage: Remove snprintf() from sysfs call-backs and replace with sysfs_emit()

Since snprintf() has the documented, but still rather strange trait of
returning the length of the data that *would have been* written to the
array if space were available, rather than the arguably more useful
length of data *actually* written, it is usually considered wise to use
something else instead in order to avoid confusion.

In the case of sysfs call-backs, new wrappers exist that do just that.

Link: https://lwn.net/Articles/69419/
Link: https://github.com/KSPP/linux/issues/105
Cc: Alan Stern <stern@rowland.harvard.edu>
Cc:  <usb-storage@lists.one-eyed-alien.net>
Signed-off-by: Lee Jones <lee@kernel.org>
Acked-by: Alan Stern <stern@rowland.harvard.edu>
Link: https://lore.kernel.org/r/20231213164246.1021885-13-lee@kernel.orgSigned-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/usb/storage/sierra_ms.c

@@ -98,26 +98,26 @@ static ssize_t truinst_show(struct device *dev, struct device_attribute *attr,
 	struct usb_device *udev = interface_to_usbdev(intf);
 	int result;
 	if (swi_tru_install == TRU_FORCE_MS) {
-		result = snprintf(buf, PAGE_SIZE, "Forced Mass Storage\n");
+		result = sysfs_emit(buf, "Forced Mass Storage\n");
 	} else {
 		swocInfo = kmalloc(sizeof(struct swoc_info), GFP_KERNEL);
 		if (!swocInfo) {
-			snprintf(buf, PAGE_SIZE, "Error\n");
+			sysfs_emit(buf, "Error\n");
 			return -ENOMEM;
 		}
 		result = sierra_get_swoc_info(udev, swocInfo);
 		if (result < 0) {
 			dev_dbg(dev, "SWIMS: failed SWoC query\n");
 			kfree(swocInfo);
-			snprintf(buf, PAGE_SIZE, "Error\n");
+			sysfs_emit(buf, "Error\n");
 			return -EIO;
 		}
 		debug_swoc(dev, swocInfo);
-		result = snprintf(buf, PAGE_SIZE,
-			"REV=%02d SKU=%04X VER=%04X\n",
-			swocInfo->rev,
-			swocInfo->LinuxSKU,
-			swocInfo->LinuxVer);
+		result = sysfs_emit(buf,
+				    "REV=%02d SKU=%04X VER=%04X\n",
+				    swocInfo->rev,
+				    swocInfo->LinuxSKU,
+				    swocInfo->LinuxVer);
 		kfree(swocInfo);
 	}
 	return result;