mem-cache: print when hitting on a prefetched line
mem-cache: print when hitting on a prefetched line

Only print it on the first it on a prefetched line
(as the prefetched flag is removed after the first hit)
This is useful when debugging prefetchers.

Change-Id: Id67cc957c7366a244bedad93824a3c4fdf2055b5
Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/47601
Tested-by: kokoro <2ac7b1f3fa578934c95181d4272be0d3bca00121@google.com>
Reviewed-by: Nikos Nikoleris <b6a1b3cd9d36c44e9eeb16bc870df3cb2a0cf469@arm.com>
Reviewed-by: Daniel Carvalho <91779fc734d358d9575ec4910de29bfcbcaf1b22@yahoo.com.br>
Maintainer: Daniel Carvalho <91779fc734d358d9575ec4910de29bfcbcaf1b22@yahoo.com.br>

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