arch: Remove the mt.hh switching header.

This header was only useful in MIPS and is only used internally within
MIPS. It doesn't need to be a switching header file.

Change-Id: Id7005f73b95e122f9ab83b3b657cae3391682f26
Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/18468
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