drivers:net:fsl-mc: Update MC address calculation

drivers:net:fsl-mc: Update MC address calculation

Update MC address calculation as per MC design requirement of address
as least significant 512MB address of MC private allocated memory,
i.e. address should point to end address masked with 512MB offset in
private DRAM block.

Signed-off-by: Priyanka Jain <priyanka.jain@nxp.com>
Signed-off-by: Ashish Kumar <ashish.kumar@nxp.com>
[YS: reformatted commit message]
Reviewed-by: York Sun <york.sun@nxp.com>