hash/crc32: remove single-use {castagnoli,ieee}ArchImpl bools
hash/crc32: remove single-use {castagnoli,ieee}ArchImpl bools

These are only used once right after being set in castagnoliInit and
ieeeInit, respectively.

Change-Id: Ifc5df1fe3040b97b1d252cc6d6d28d8fbc132fa5
Reviewed-on: https://go-review.googlesource.com/c/go/+/423854
TryBot-Result: Gopher Robot <66cb808b70d30c07676d5e946fee83fd561249e5@golang.org>
Reviewed-by: Ian Lance Taylor <87e9c6d529889242b7e184afb632328636553ab4@google.com>
Reviewed-by: Bryan Mills <1c8aad60184261ccede67f5c63a0d2a3bf3c9ff4@google.com>
Auto-Submit: Tobias Klauser <0a68dd4915066ec5d3f81f75a828fee53dcc8822@gmail.com>
Run-TryBot: Tobias Klauser <0a68dd4915066ec5d3f81f75a828fee53dcc8822@gmail.com>

golang/go,golang/go,golang/go,golang/go,golang/go,golang/go,golang/go,golang/go