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>
diff --git a/drivers/net/Kconfig b/drivers/net/Kconfig
index 084e095..aaf10a2 100644
--- a/drivers/net/Kconfig
+++ b/drivers/net/Kconfig
@@ -1,5 +1,6 @@
 source "drivers/net/phy/Kconfig"
 source "drivers/net/pfe_eth/Kconfig"
+source "drivers/net/fsl-mc/Kconfig"
 
 config DM_ETH
 	bool "Enable Driver Model for Ethernet drivers"