PPC: MPIC: Remove read functionality for WO registers

The IPI dispatch registers are write only according to every MPIC
spec I have found. So instead of pretending you could read back something
from them, better not handle them at all.
Reported-by: NElie Richa <richa@adacore.com>
Signed-off-by: NAlexander Graf <agraf@suse.de>

hw/openpic.c

@@ -952,13 +952,6 @@ static uint32_t openpic_cpu_read_internal(void *opaque, target_phys_addr_t addr,
     case 0xB0: /* PEOI */
         retval = 0;
         break;
-#if MAX_IPI > 0
-    case 0x40: /* IDE */
-    case 0x50:
-        idx = (addr - 0x40) >> 4;
-        retval = read_IRQreg(opp, opp->irq_ipi0 + idx, IRQ_IDE);
-        break;
-#endif
     default:
         break;
     }