mtd: rawnand: brcmnand: fix sparse warnings

Fix the following sparse warnings:
sparse warnings: (new ones prefixed by >>)
>> drivers/mtd/nand/raw/brcmnand/bcmbca_nand.c:79:41: sparse: sparse:
cast removes address space '__iomem' of expression
   drivers/mtd/nand/raw/brcmnand/bcmbca_nand.c:80:17: sparse: sparse:
cast removes address space '__iomem' of expression
   drivers/mtd/nand/raw/brcmnand/bcmbca_nand.c:80:17: sparse: sparse:
cast removes address space '__iomem' of expression
   drivers/mtd/nand/raw/brcmnand/bcmbca_nand.c:80:17: sparse: sparse:
cast removes address space '__iomem' of expression

Fixes: c52c16d1bee5 ("mtd: rawnand: brcmnand: Add BCMBCA read data bus interface")
Reported-by: kernel test robot <lkp@intel.com>
Closes: https://lore.kernel.org/oe-kbuild-all/202402270940.gmVLVRg0-lkp@intel.com/
Signed-off-by: William Zhang <william.zhang@broadcom.com>
Signed-off-by: Miquel Raynal <miquel.raynal@bootlin.com>
Link: https://lore.kernel.org/linux-mtd/20240227190258.200929-1-william.zhang@broadcom.com