Finish conversion CONFIG_SYS_NAND_SELF_INIT to Kconfig

In order to finish this conversion we need to add a symbols for
SPL_SYS_NAND_SELF_INIT and TPL_SYS_NAND_SELF_INIT as there are cases
there where we need to, or need to not, use that framework as things
stand.

Signed-off-by: Tom Rini <trini@konsulko.com>