chore: add CHANGELOG entry on support of ARM systems with big caches

#4869 changed the
type that holds the number of sets of a CPU cache from `u16` to `u32`.
This allows us to support ARM systems with CPU caches with sets more
than `u16::MAX`.

Add a CHANGELOG entry for this change

Signed-off-by: Babis Chalios <bchalios@amazon.es>

Author: bchalios

CHANGELOG.md

@@ -23,6 +23,9 @@ and this project adheres to
   set, it won't trigger the lockup condition. Calling the ioctl for guests that
   don't use kvmclock will fail. These failures are not fatal. We log the failure
   and increase the `vcpu.kvmclock_ctrl_fails` metric.
+- [#4869](https://github.com/firecracker-microvm/firecracker/pull/4869): Added
+  support for Aarch64 systems which feature CPU caches with a number of sets
+  higher than `u16::MAX`.
 
 ### Changed