staging: fsl-mc: add support for the modalias sysfs attribute

In order to support uevent based module loading implement modalias support
for the fsl-mc bus driver. Aliases are based on vendor and object/device
id and are of the form "fsl-mc:vNdN".

Signed-off-by: Stuart Yoder <stuart.yoder@nxp.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>