arch: Rename PCStateCommon to PCStateWithNext.
arch: Rename PCStateCommon to PCStateWithNext.

This intermediate class has a fairly vague name. This new name more
specifically describes what this PCState class adds to its base class.

Change-Id: I6d19383f3eb2895d924187ddbf8185352db71542
Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/52486
Tested-by: kokoro <2ac7b1f3fa578934c95181d4272be0d3bca00121@google.com>
Reviewed-by: Daniel Carvalho <91779fc734d358d9575ec4910de29bfcbcaf1b22@yahoo.com.br>
Maintainer: Daniel Carvalho <91779fc734d358d9575ec4910de29bfcbcaf1b22@yahoo.com.br>

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