No. You can not use the GPS from your iPhone with your non-GPS equipped iPad when connected via a hotspot. GPS position data is not sent through a hotspot.
To receive GPS position information on an iPad, you will need either a wifi+cellular iPad (these include an integrated GPS chip) or an external GPS source such as Sentry, Sentry mini, or a Garmin panel connection.
For more guidance on which devices will work best with ForeFlight, check out our iPad and device buying guide