mem-cache: Remove old todo about latency in hit function

mem-cache: Remove old todo about latency in hit function

The header and payload delay have already been accounted and
zeroed previous to calling this function. The probe is not
allowed to modify the packet, therefore no extra delays are
added, and it is safe to remove the todo note.

Change-Id: I8ddf7e189fbe609cdec34364f3c013427930daf7
Signed-off-by: Daniel R. Carvalho <odanrc@yahoo.com.br>
Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/14875
Reviewed-by: Nikos Nikoleris <nikos.nikoleris@arm.com>
Maintainer: Nikos Nikoleris <nikos.nikoleris@arm.com>