haven: Include notifer header file

The haven RM driver header file exposes functions where notifier
blocks are used. However, not all clients who include the
header file will necessarily have the notifier header file
in their source file, which causes compilation errors. Thus,
include the notifier header file in the RM driver header file
so that all other clients don't have to.

Change-Id: If74509e5d7fc2bbaeb4a427a7cd576f853fd8358
Signed-off-by: Isaac J. Manjarres <isaacm@codeaurora.org>