[sram_ctrl] Reduce number of PRINCE half rounds for main SRAM scrambling

[vogelpi]

Description

After cleaning up timing constraints and exclusions, the PD team noticed that further optimizations on the design are required for timing closure.

Reducing the number of PRINCE half rounds for the main SRAM scrambling back to the level in Earlgrey ES was identified as a way to ease this. From a security perspective, 5 full PRINCE rounds (instead of 7) have been found acceptable.

Since ES, we number of scrambling rounds have been adjusted using the following PRs:

• [prim, rom_ctrl] Increase number of PRINCE rounds for improved security #22425
• [rv_core_ibex] Re-vendor Ibex and reduce number of PRINCE rounds for ICache scrambling #22948

[vogelpi]

I am closing this again as both the PR integrating this change into master (#24447) as well as the cherry-pick PR into the tapeout release branch (#24378) have been merged.