sim: Eliminate the generic PseudoInstABI.
sim: Eliminate the generic PseudoInstABI.

Calls to gem5 ops are now handled by locally defined ABIs in each of the
ISAs that support them.

Change-Id: I30aac7b49fa8dc8e18aa7724338d1fd2adacda90
Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/39319
Reviewed-by: Jason Lowe-Power <92de577f37050ad05b60626d2f17913f40dcb1a2@gmail.com>
Maintainer: Gabe Black <d3e8afea784ab4a50a2dbf9149d2eaa8478e1cbc@gmail.com>
Tested-by: kokoro <2ac7b1f3fa578934c95181d4272be0d3bca00121@google.com>

gem5/gem5,gem5/gem5,gem5/gem5,gem5/gem5,gem5/gem5,gem5/gem5,gem5/gem5