serial: allow callback setting to be exclusive

Both the IRQ API and Asynchronous API support callback.
However, since they are both interrupt driven, having
callbacks on both API would interfere with each other
in almost all cases. So this adds a kconfig to signal
that the callbacks should be exclusive to each other.
In other words, if one is set, the other should not
be active. Drivers implementing both APIs have been
updated to remove the callbacks from the other API.
Though, this still leaves the option to disable
the kconfig and allows both APIs to have callbacks
if one desires.

Fixes #48606

Signed-off-by: Daniel Leung <daniel.leung@intel.com>