mor1kx-sprs: add DRR definitions
ctrl prontoespresso: add DRR functionality, fix NPC writing logic

DRR[TE] is now set on software breakpoint.

A register which held the written NPC was redundant and has been removed
ctrl espresso: add software breakpoint functionality

Cause l.trap with DSR[TE] set to stall the processor
mor1kx top-level: enable add-with-carry support and overflow detection by default