mem-cache: Move unused prefetches counter update
mem-cache: Move unused prefetches counter update

The number of unused prefetches should be updated every time
a block is invalidated, therefore we move the update to within
the corresponding function.

Change-Id: If3ac2ea43611525bd3c36d628d88382042fcb7dc
Signed-off-by: Daniel R. Carvalho <91779fc734d358d9575ec4910de29bfcbcaf1b22@yahoo.com.br>
Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/18908
Tested-by: kokoro <2ac7b1f3fa578934c95181d4272be0d3bca00121@google.com>
Reviewed-by: Nikos Nikoleris <b6a1b3cd9d36c44e9eeb16bc870df3cb2a0cf469@arm.com>
Maintainer: Nikos Nikoleris <b6a1b3cd9d36c44e9eeb16bc870df3cb2a0cf469@arm.com>

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