ppc4xx: correct SDRAM controller warning message condition

The message "Truncating memory to %d MiB to fit SDRAM controller limits"
should be displayed only when a user chooses an amount of RAM which
can't be represented by the PPC 4xx SDRAM controller (e.g. 129MB, which
would only be valid if the controller supports a bank size of 1MB).
Signed-off-by: NHollis Blanchard <hollis@penguinppc.org>

hw/ppc4xx_devs.c

@@ -684,7 +684,7 @@ ram_addr_t ppc4xx_sdram_adjust(ram_addr_t ram_size, int nr_banks,
     }
 
     ram_size -= size_left;
-    if (ram_size)
+    if (size_left)
         printf("Truncating memory to %d MiB to fit SDRAM controller limits.\n",
                (int)(ram_size >> 20));