arch: arm: Remove extraneous root cmake files

The ARM architecture root directory contains `aarch32.cmake` and
`aarch64.cmake` files whose contents are better suited to go into other
more purpose-specific files.

This commit removes the aforementioned files and moves their contents
to other files following the convention used by other architectures.

Signed-off-by: Stephanos Ioannidis <root@stephanos.io>
4 files changed