kernel: include: heartbeat: Add no-op implementation

Add declaration for heartbeat driver when it is enabled.
Provide a no-operation (no-op) definition when the
heartbeat driver is disabled to ensure no action is performed.

Change-Id: I7868a41fc60c4583ba87051f600ceb085f1e2087
Signed-off-by: kammarih <quic_kammarih@quicinc.com>