mtd: rawnand: brcmnand: Fix sparse warnings in bcma_nand

sparse was unhappy about the way we woulc call cpu_to_be32/be32_to_cpu,
apply the appropriate casting to silence the warnings.

Reported-by: kernel test robot <lkp@intel.com>
Link: https://lists.01.org/hyperkitty/list/kbuild-all@lists.01.org/thread/ZNHPJFYLO64EGI5QUT7HZ63J7O5J2G7N/


Signed-off-by: Florian Fainelli <f.fainelli@gmail.com>
Signed-off-by: Miquel Raynal <miquel.raynal@bootlin.com>
Link: https://lore.kernel.org/linux-mtd/20220125225243.15201-1-f.fainelli@gmail.com