cpu: Use the newly promoted uReset in the minor CPU.
cpu: Use the newly promoted uReset in the minor CPU.

Rather than use an #if THE_ISA check to see if the CPU can use the
microPC accessirs, this change uses the newly promoted/exposed uReset
for the same purpose.

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

Change-Id: I4ac931624a2c8e2bbcd5189a05d9ec174bd03d4a
Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/48705
Reviewed-by: Hoa Nguyen <a0aa8449aacb303edcb25d6bbe69da9124f010fc@ucdavis.edu>
Maintainer: Gabe Black <d3e8afea784ab4a50a2dbf9149d2eaa8478e1cbc@gmail.com>
Tested-by: kokoro <2ac7b1f3fa578934c95181d4272be0d3bca00121@google.com>

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