arm: imx: Finish migration of CONFIG_CSF_SIZE to Kconfig

While the normal case of CSF_SIZE is handled via Kconfig we have entries
in config headers related to CONFIG_SECURE_BOOT.  However in commit
d714a75f ("imx: replace CONFIG_SECURE_BOOT with CONFIG_IMX_HAB")
this was renamed to CONFIG_IMX_HAB.  Update the CSF_SIZE entry to have
the correct default value if we have IMX_HAB enabled.

Cc: Stefano Babic <sbabic@denx.de>
Cc: Fabio Estevam <festevam@gmail.com>
Cc: NXP i.MX U-Boot Team <uboot-imx@nxp.com>
Fixes: d714a75f ("imx: replace CONFIG_SECURE_BOOT with CONFIG_IMX_HAB")
Signed-off-by: Tom Rini <trini@konsulko.com>