staging: Fix error return code in vboxsf_fill_super()

Fix to return negative error code -ENOMEM from the error handling
case instead of 0, as done elsewhere in this function.

Fixes: df402865 ("staging: Add VirtualBox guest shared folder (vboxsf) support")
Signed-off-by: Wei Yongjun <weiyongjun1@huawei.com>
Reviewed-by: Hans de Goede <hdegoede@redhat.com>
Link: https://lore.kernel.org/r/20191106115954.114678-1-weiyongjun1@huawei.comSigned-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/staging/vboxsf/super.c

@@ -176,8 +176,10 @@ static int vboxsf_fill_super(struct super_block *sb, struct fs_context *fc)
 	/* Turn source into a shfl_string and map the folder */
 	size = strlen(fc->source) + 1;
 	folder_name = kmalloc(SHFLSTRING_HEADER_SIZE + size, GFP_KERNEL);
-	if (!folder_name)
+	if (!folder_name) {
+		err = -ENOMEM;
 		goto fail_free;
+	}
 	folder_name->size = size;
 	folder_name->length = size - 1;
 	strlcpy(folder_name->string.utf8, fc->source, size);