fsl-mc: add helper macro to determine if a device is of fsl_mc type

Add a helper macro to return if a device has a bus type of fsl_mc.
This makes the bus driver code more readable and provides a way for
drivers like the SMMU driver to easily check the bus type.

Signed-off-by: Nipun Gupta <nipun.gupta@nxp.com>
Signed-off-by: Bharat Bhushan <bharat.bhushan@nxp.com>
Acked-by: Stuart Yoder <stuart.yoder@nxp.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>