dev-arm: Rewrite SMMUv3 Commands

dev-arm: Rewrite SMMUv3 Commands

This patch is rewriting the SMMUv3::processCommand method for the
following reasons:

* Command names were not matching spec
* Command encoding/opcode was wrong

The patch is not adding any new command: there is still a subset of
unimplemented commands; those are:

* CMD_TLBI_EL3_ALL
* CMD_TLBI_EL3_VA
* CMD_TLBI_EL2_ALL
* CMD_TLBI_EL2_VA
* CMD_TLBI_EL2_VAA
* CMD_TLBI_EL2_ASID

which require StreamWorld support, and

* CMD_ATC_INV
* CMD_PRI_RESP
* CMD_RESUME
* CMD_STALL_TERM

which require in sequence: ATS, PRI, Stall Model support

Change-Id: Ia2dd47b5588738402d9584a00cfc88c94c253ad0
Signed-off-by: Giacomo Travaglini <giacomo.travaglini@arm.com>
Reviewed-by: Michiel van Tol <michiel.vantol@arm.com>
Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/19668
Reviewed-by: Andreas Sandberg <andreas.sandberg@arm.com>
Maintainer: Andreas Sandberg <andreas.sandberg@arm.com>
Tested-by: kokoro <noreply+kokoro@google.com>