mtd: rawnand: fsl_ifc: Add an __iomem specifier on eccstat_regs

The local eccstat_regs variable in fsl_ifc_run_command() is missing an
__iomem specifier, and sparce complains about that.

Signed-off-by: Boris Brezillon <boris.brezillon@bootlin.com>
Signed-off-by: Miquel Raynal <miquel.raynal@bootlin.com>