base: Include some required headers in amo.hh.

base: Include some required headers in amo.hh.

amo.hh was using several non-default definitions including
std::function, uint8_t, and std::array without including any headers
at all, and instead apparently relying on those having already been
brought in by an earlier include.

This change adds those includes explicitly.

Change-Id: I92166ff581e74bd705e10fd4fa454df179ae1a97
Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/24183
Reviewed-by: Giacomo Travaglini <giacomo.travaglini@arm.com>
Maintainer: Giacomo Travaglini <giacomo.travaglini@arm.com>
Tested-by: kokoro <noreply+kokoro@google.com>