[llvm] [M68k][GISel] Fix buildbot failure caused by additional MIFlags (PR #151147)

[Fabian Ritter via llvm-commits]

ritter-x2a wrote:

Merging without waiting for the pre-merge CI tests to finish; those don't run the tests for the experimental M68k backend anyway.

https://github.com/llvm/llvm-project/pull/151147