Here are five possible code completions for the given function:

**Option 1: Using sprintf**
```c
static int remove_device_files(struct super_block *sb,
			       struct qib_devdata *dd)
{
	struct dentry *dir;
	char unit[10];

	/* Create a string for the unit number */
	sprintf(unit, "%d", dd->unit);

	/* Remove device files */
	dir = sb->s_root->d_subdirs;
	while (dir) {
		if (strcmp(dir->d_name.name, unit) == 0) {
			/* Remove the directory entry */
			d_delete(dir);
			break;
		}
		dir = dir->d_next;
	}

	return 0;
}
```

**Option 2: Using snprintf**
```c
static int remove_device_files(struct super_block *sb,
			       struct qib_devdata *dd)
{
	struct dentry *dir;
	char unit[10];

	/* Create a string for the unit number */
	snprintf(unit, sizeof(unit), "%d", dd->unit);

	/* Remove device files */
	dir = sb->s_root->d_subdirs;
	while (dir) {
		if (strcmp(dir->d_name.name, unit) == 0) {
			/* Remove the directory entry */
			d_delete(dir);
			break;
		}
		dir = dir->d_next;
	}

	return 0;
}
```

**Option 3: Using itoa**
```c
static int remove_device_files(struct super_block *sb,
			       struct qib_devdata *dd)
{
	struct dentry *dir;
	char unit[10];

	/* Create a string for the unit number */
	itoa(dd->unit, unit, 10);

	/* Remove device files */
	dir = sb->s_root->d_subdirs;
	while (dir) {
		if (strcmp(dir->d_name.name, unit) == 0) {
			/* Remove the directory entry */
			d_delete(dir);
			break;
		}
		dir = dir->d_next;
	}

	return 0;
}
```

**Option 4: Using string formatting with a buffer size check**
```c
static int remove_device_files(struct super_block *sb,
			       struct qib_devdata *dd)
{
	struct dentry *dir;
	char unit[10];

	/* Create a string for the unit number */
	if (snprintf(unit, sizeof(unit), "%d", dd->unit) >= sizeof(unit)) {
		/* Handle buffer overflow error */
		return -EINVAL;
	}

	/* Remove device files */
	dir = sb->s_root->d_subdirs;
	while (dir) {
		if (strcmp(dir->d_name.name, unit) == 0) {
			/* Remove the directory entry */
			d_delete(dir);
			break;
		}
		dir = dir->d_next;
	}

	return 0;
}
```

**Option 5: Using a more secure string formatting function**
```c
static int remove_device_files(struct super_block *sb,
			       struct qib_devdata *dd)
{
	struct dentry *dir;
	char unit[10];

	/* Create a string for the unit number */
	if (scnprintf(unit, sizeof(unit), "%d", dd->unit) < 0) {
		/* Handle error */
		return -EINVAL;
	}

	/* Remove device files */
	dir = sb->s_root->d_subdirs;
	while (dir) {
		if (strcmp(dir->d_name.name, unit) == 0) {
			/* Remove the directory entry */
			d_delete(dir);
			break;
		}
		dir = dir->d_next;
	}

	return 0;
}
```

Note: The `scnprintf` function is a more secure version of `snprintf` that returns the number of characters that would have been written if the buffer were large enough, rather than the number of characters actually written. This can help prevent buffer overflow errors.