platforms: ihpsg13g2: Add IO cells to DONT_USE_CELLS

Yosys started to add the IHP IO cells as standard cells and
global placement fails with:
  [ERROR RSZ-2001] failed bnet construction for _078639_/p2c

Add 'sg13g2_IOPad*' to DONT_USE_CELLS to make sure Yosys won't
use those cells.

Signed-off-by: Daniel Schultz <[email protected]>

Author: dnltz

flow/platforms/ihp-sg13g2/config.mk

@@ -41,7 +41,8 @@ export DONT_USE_CELLS += \
 sg13g2_lgcp_1 \
 sg13g2_sighold \
 sg13g2_slgcp_1 \
-sg13g2_dfrbp_2
+sg13g2_dfrbp_2 \
+sg13g2_IOPad*
 
 
 # Define fill cells