util: Break out the dispatch tables in the m5 util call types.

util: Break out the dispatch tables in the m5 util call types.

These dispatch tables will be useful in the java and lua wrappers as
well, since those should also support the alternative call methods.

Change-Id: Ib3be510c99b04960eb2efbc732aebe3165882bee
Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/28178
Reviewed-by: Gabe Black <gabe.black@gmail.com>
Reviewed-by: Anthony Gutierrez <anthony.gutierrez@amd.com>
Maintainer: Gabe Black <gabe.black@gmail.com>
Tested-by: kokoro <noreply+kokoro@google.com>