mem: Remove a check that the memory size is a multiple of the page size.

mem: Remove a check that the memory size is a multiple of the page size.

There are a few problems with this check.

1. Many ISAs support multiple page sizes.
2. Memories (particularly small ROMs) may not actually be in multiples
   of the page size.
3. In a heterogenous environment, there won't be a single page size even
   if each ISA picks a canonical page size.
4. Other than catching some egregious configuration mistakes, there's
   nothing functionally wrong/different about a memory that isn't evenly
   coverable in pages, especially in systems or configurations that
   don't even use paging.

Change-Id: I3cd241657318d2e3fd5a1226cb54fdebbf172788
Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/26423
Maintainer: Gabe Black <gabeblack@google.com>
Maintainer: Jason Lowe-Power <power.jg@gmail.com>
Reviewed-by: Jason Lowe-Power <power.jg@gmail.com>
Tested-by: Gem5 Cloud Project GCB service account <345032938727@cloudbuild.gserviceaccount.com>