Update aesd_ioctl.h

Move reference to ioctl number to match latest location in the kernel source

aesd-char-driver/aesd_ioctl.h

@@ -33,7 +33,7 @@ struct aesd_seekto {
     uint32_t write_cmd_offset;
 };
 
-// Pick an arbitrary unused value from https://github.com/torvalds/linux/blob/master/Documentation/ioctl/ioctl-number.rst
+// Pick an arbitrary unused value from https://github.com/torvalds/linux/blob/master/Documentation/userspace-api/ioctl/ioctl-number.rst
 #define AESD_IOC_MAGIC 0x16
 
 // Define a write command from the user point of view, use command number 1