rtems/score/object.h: Include <rtems/score/cpu.h> to honor 16-bit Ids

Selection of 16-bit object Ids is a port specific decision. Somewhere
along the way, the file providing this information was dropped from
the include file set. This resulted in the code being compiled with
a mix of 16 and 32 bit ID assumptions for those targets with 16-bit Ids.
h8300/cpu_asm.S: Correct register size suffix for loading DISPATCH_NEEDED
h8300/h8sim/startup/__main.c: Removed. Obsolete remnant of COFF.
h8300/h8sim: Exit simulator cleanly