Fix handling of 32bit IMM in %addi on 32bit machines
Fix handling of 32bit IMM in %addi on 32bit machines

The handling of immediate add used to do 16bits at a time. When it went
up to 32bits, the need to work in chunks vanished, but the chunk handling
was still there, this time shifting by 32, which causes problems on 32bit
machines. Simplify the %addi handling to avoid this.
themperek/iverilog,CastMi/iverilog,CastMi/iverilog,themperek/iverilog,CastMi/iverilog,themperek/iverilog