staging: fsl-mc: Convert documentation to rst format

Update the doc file to comply with the rst format.

It's not integrated into the documentation build structure yet,
since it's still located in drivers/staging.

Signed-off-by: Ioana Radulescu <ruxandra.radulescu@nxp.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>