treewide: Add FhG SPU

[rfiorani]

Adds FhG SPU rtl to the repo.

In summary:

• Instantiates the fhg_spu_tile module in the picobello_top
• Adds it to the floonoc configuration file
• Adds a dummy tile for rtl compilation without asic target
• Adds a local dependency in Bender.yml
• Edits the make file to clone the SPU rtl from private repo (like for PD repo)
• Updates the PD repo commit

[fischeti]

Nice work! thanks a lot