drivers/fsl-mc: Create Kconfig file to manage driver specific configs better

Create drivers/net/fsl-mc/Kconfig and move fsl-mc specific configs
from arch/arm/cpu/armv8/fsl-layerscape/Kconfig to this new Kconfig

Signed-off-by: Florinel Iordache <florinel.iordache@nxp.com>
Acked-by: Joe Hershberger <joe.hershberger@ni.com>