arm: mx6: Fix missing Kconfig option for Novena

Add two missing Kconfig options for Novena and drop the SPL
from the Novena config.

Signed-off-by: Marek Vasut <marex@denx.de>
Cc: Stefano Babic <sbabic@denx.de>
Cc: Sean Cross <xobs@kosagi.com>
Cc: Marek Vasut <marex@denx.de>
Cc: Fabio Estevam <fabio.estevam@freescale.com>