arm: Call pseudoInst directly from the mmapped IPR handlers.

arm: Call pseudoInst directly from the mmapped IPR handlers.

The amount of plumbing necessary for the generic IPR mechanism out
weighs its value, considering it's only used for the m5ops.

Jira Issue: https://gem5.atlassian.net/browse/GEM5-187

Change-Id: I0efcf43904d5f779bef5ad127dd8d39fff41ac39
Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/23185
Reviewed-by: Gabe Black <gabeblack@google.com>
Maintainer: Gabe Black <gabeblack@google.com>
Maintainer: Giacomo Travaglini <giacomo.travaglini@arm.com>
Tested-by: kokoro <noreply+kokoro@google.com>