DT headers already define NOOP routines when CONFIG_OF is not defined.

[jarkko.sakkinen@linux.intel.com: I tested that the driver compiles
 without warnings and errors with and without CONFIG_OF flag.]
Signed-off-by: Christophe Ricard <christophe-h.ricard@st.com>
Reviewed-by: Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com>
Tested-by: Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com>
Signed-off-by: Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com>