No. The reason mechanical drives needed defragmentation was to speed up file access.
When saving and deleting files on a hard drive, you start getting broken up files in different areas of the hard drive due to how files are saved. When reading a file a mechanical drive needs to move to all the locations on the platters to get the completed file. Over time, files may get split up more and more, and farther and farther. This means the needle needs to travel more to get a completed file. This is what creates the slowness.
Defragmenting simply tries to put the file parts together as much as possible so the needle does not need to go around reading parts of file. Its all on the same place, so reading is done continuously, and quicker.
On an SSD, this is not an issue. The files still can get broken into parts, and scattered, but access to the files does not take longer or shorter. Access on a SSD is exactly the same to any part of the drive. So accessing 5 parts of a file will take the same amount of time whether they are together or not.
There is no point in defragmenting an SSD, and in fact it can lead to shorten life span of an SSD, since you are using write cycles on it.
Again, Do not Defragment a solid state drive. either on an iPad or on a computer.
Rebooting the iPad will clear memory, and other OS temp files. but will do nothing to the file structure on its internal storage.