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 Scout or Stratus.
For more guidance on which devices will work best with ForeFlight, check out our iPad and device buying guide