python: Remove unnecessary exports from pybind enums
python: Remove unnecessary exports from pybind enums

According to pybind documentation [1], enum entries use
.export_values() to export the enum entries into the parent
scope. However, strongly typed C++11 class enums are in their own
scope and therefore do not need to be exported.

[1]: https://pybind11.readthedocs.io/en/stable/classes.html#enume
rations-and-internal-types

Change-Id: I6181306b530d59eaedcb3daf9cab0a03d01d56f4
Signed-off-by: Nikos Nikoleris <b6a1b3cd9d36c44e9eeb16bc870df3cb2a0cf469@arm.com>
Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/25709
Reviewed-by: Jason Lowe-Power <68c46a606457643eab92053c1c05574abb26f861@lowepower.com>
Maintainer: Gabe Black <5c8aa1266c03186393d9e7b3b4e3b14239af8201@google.com>
Tested-by: kokoro <2ac7b1f3fa578934c95181d4272be0d3bca00121@google.com>

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