dev: Clean up the IDE disk and controller classes a little.

Fix some style issues, and replace some if () panics with panic_ifs.

Change-Id: Ic4fae016520e43d32f435bf3fc0ec37df25ca02a
Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/55583
Reviewed-by: Andreas Sandberg <andreas.sandberg@arm.com>
Maintainer: Andreas Sandberg <andreas.sandberg@arm.com>
Tested-by: kokoro <noreply+kokoro@google.com>
3 files changed