board: freescale: p1_p2_rdb_pc: Define SW macros for lower and upper NOR banks

Replace hardcoded i2c hex values for NOR banks by named SW macros in
map_lowernorbank/map_uppernorbank env commands.

Signed-off-by: Pali Rohár <pali@kernel.org>
Reviewed-by: Priyanka Jain <priyanka.jain@nxp.com>