LSU PMA support

Created by: silabs-oysteink

PMA/MPU work by silabs-oivind, controller and plumbing by silabs-oysteink.

• Implements PMA check for misaligned load/store to IO regions
• Implements support for LSU PMA exceptions.
• Suppresses ex_wb_pipe.rf_we for first half of misaligned LSU instructions (only second half will write to RF)
• Suppresses WB stage rf_we in case of PMA errors.