RFC [reload1] maybe share op_addr reloads

[DJ Delorie]

This comment seems to explain why:

  /* Scan all the reloads, and check for RELOAD_FOR_OPERAND_ADDRESS reloads.
     If we have more than one, then convert all RELOAD_FOR_OPADDR_ADDR
     reloads to RELOAD_FOR_OPERAND_ADDRESS reloads.

     choose_reload_regs assumes that RELOAD_FOR_OPADDR_ADDR reloads never
     conflict with RELOAD_FOR_OPERAND_ADDRESS reloads.  This is true for a
     single pair of RELOAD_FOR_OPADDR_ADDR/RELOAD_FOR_OPERAND_ADDRESS reloads.
     However, if there is more than one RELOAD_FOR_OPERAND_ADDRESS reload,
     then a RELOAD_FOR_OPADDR_ADDR reload conflicts with all
     RELOAD_FOR_OPERAND_ADDRESS reloads other than the one that uses it.
     This is complicated by the fact that a single operand can have more
     than one RELOAD_FOR_OPERAND_ADDRESS reload.  It is very difficult to fix
     choose_reload_regs without affecting code quality, and cases that
     actually fail are extremely rare, so it turns out to be better to fix
     the problem here by not generating cases that choose_reload_regs will
     fail for.  */

This extremely rare case happens to be the case that's failing for
m32c :-P

Maybe we can conditionalize the new logic with SMALL_REGISTER_CLASSES?