mem-cache: Rename Prefetcher namespace as prefetch

As part of recent decisions regarding namespace
naming conventions, all namespaces will be changed
to snake case.

::Prefetcher became ::prefetcher.

"prefetch" was chosen over "prefetcher" to avoid generating
conflicts with the already existing variables. "prefetcher"
is a name that is expected to be more common in user's code
than "prefetch".

Change-Id: I8f07217f278a0229e05545b7847f2620ed208c66
Signed-off-by: Daniel R. Carvalho <odanrc@yahoo.com.br>
Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/45410
Maintainer: Jason Lowe-Power <power.jg@gmail.com>
Tested-by: kokoro <noreply+kokoro@google.com>
Reviewed-by: Hoa Nguyen <hoanguyen@ucdavis.edu>

src/mem/cache/prefetch/irregular_stream_buffer.cc

@@ -32,7 +32,9 @@
 #include "mem/cache/prefetch/associative_set_impl.hh"
 #include "params/IrregularStreamBufferPrefetcher.hh"
 
-namespace Prefetcher {
+GEM5_DEPRECATED_NAMESPACE(Prefetcher, prefetch);
+namespace prefetch
+{
 
 IrregularStreamBuffer::IrregularStreamBuffer(
     const IrregularStreamBufferPrefetcherParams &p)
@@ -208,4 +210,4 @@ IrregularStreamBuffer::addStructuralToPhysicalEntry(
     mapping.counter++;
 }
 
-} // namespace Prefetcher
+} // namespace prefetch