mtd: fsl_ifc_nand: fix sparse warnings

drivers/mtd/nand/fsl_ifc_nand.c:196:34: warning: cast removes address space of expression [sparse]
drivers/mtd/nand/fsl_ifc_nand.c:196:34: warning: incorrect type in initializer (different address spaces) [sparse]
drivers/mtd/nand/fsl_ifc_nand.c:196:34:    expected unsigned int [noderef] [usertype] <asn:2>*mainarea [sparse]
drivers/mtd/nand/fsl_ifc_nand.c:196:34:    got unsigned int [usertype] *<noident> [sparse]
...

Signed-off-by: Kim Phillips <kim.phillips@freescale.com>
Signed-off-by: Artem Bityutskiy <artem.bityutskiy@linux.intel.com>
Signed-off-by: David Woodhouse <David.Woodhouse@intel.com>