[topgen] Derive IP template paths from script path instead of output path
[topgen] Derive IP template paths from script path instead of output path

Deriving the IP template paths from the specified output path only works
if the output path is in the same hierarchy.

Signed-off-by: Pirmin Vogel <386a7fc8e7338ed7899b4d9883c0ebec5de81366@lowrisc.org>

lowRISC/opentitan,lowRISC/opentitan,lowRISC/opentitan,lowRISC/opentitan,lowRISC/opentitan,lowRISC/opentitan