bus: removed outdated warn regarding 64 B block sizes
bus: removed outdated warn regarding 64 B block sizes

this warn is outdated as 64 B blocks are very common, and even
the default size for some CPU types. E.g., arm_detailed.

andrewfu0325/gem5-aladdin,andrewfu0325/gem5-aladdin,andrewfu0325/gem5-aladdin,andrewfu0325/gem5-aladdin,andrewfu0325/gem5-aladdin,andrewfu0325/gem5-aladdin,andrewfu0325/gem5-aladdin