This commit fixes Cortex-M header inclusions from the deprecated paths.
The Cortex-M headers were relocated from `include/arch/arm/cortex_m` to
`include/arch/arm/aarch32/cortex_m` by the refactoring done in the
commit d048faacf2.
Signed-off-by: Stephanos Ioannidis <root@stephanos.io>