arm: Make the misc reg class return the name of misc regs.
arm: Make the misc reg class return the name of misc regs.

Jira Issue: https://gem5.atlassian.net/browse/GEM5-1060

Change-Id: Ic2c8576b079c68f28b48006dd90515b1a5c68ed9
Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/48707
Reviewed-by: Hoa Nguyen <a0aa8449aacb303edcb25d6bbe69da9124f010fc@ucdavis.edu>
Maintainer: Gabe Black <d3e8afea784ab4a50a2dbf9149d2eaa8478e1cbc@gmail.com>
Tested-by: kokoro <2ac7b1f3fa578934c95181d4272be0d3bca00121@google.com>

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