I have met the same situation as you two weeks ago, but I'm on iPhone. Have you figured it out? I have tried several methods to help me out, perhaps you can get some idea from them. First is to force restart your iPad. You need to hold down the home and power button together till the apple logo appearing. But sometimes this method doesn't work for a bricked iPad.
Another way is to recover by entering the DFU mode, but this will erase all your data stored on iPad. Just plug in your iPad to PC and open iTunes. Then turn off your iPad, hold down the power and home button together till you see the Apple logo. Next, release the power button while continuing to hold the home button. Finally, wait for the iTunes to tell you that it’s in the restore mode.
By the way, there are several ways can prevent your iPad bricked during upgrading, such as use the latest version iTunes, backup all your data before upgrading, ensure a sufficient space of your iPad and so on. Hope this can give you useful clues and help you fix the bricked iPad during upgrading. Best regards!
