mtd: rawnand: nand_base: Allow base driver to be used in SPL without nand_bbt

nand_bbt.c is not being built with the nand_base driver during SPL
build. This results in build failures if we try to access any nand_bbt
related functions.

Don't use any nand_bbt functions for SPL build.

Signed-off-by: Roger Quadros <rogerq@kernel.org>
Signed-off-by: Michael Trimarchi <michael@amarulasolutions.com>
Signed-off-by: Dario Binacchi <dario.binacchi@amarulasolutions.com>
Link: https://lore.kernel.org/all/20221220102203.52398-3-rogerq@kernel.org