dev: fix device number check error in IDE controller

Fixed a typo between 3 and 4.

Change-Id: I1470e30c4d472587db0b9da5512b24ab92f1fd65
Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/64052
Tested-by: kokoro <noreply+kokoro@google.com>
Reviewed-by: Gabe Black <gabe.black@gmail.com>
Maintainer: Gabe Black <gabe.black@gmail.com>

src/dev/storage/ide_ctrl.cc

@@ -76,7 +76,7 @@ IdeController::IdeController(const Params &p)
     secondary(name() + ".secondary", this, false),
     ioShift(p.io_shift), ctrlOffset(p.ctrl_offset)
 {
-    panic_if(params().disks.size() > 3,
+    panic_if(params().disks.size() > 4,
             "IDE controllers support a maximum of 4 devices attached!");
 
     // Assign the disks to channels