media: fsl-viu: fix __iomem annotations

Those annotations are wrong, causing this warning:

    drivers/media/platform/fsl-viu.c:1440:21: warning: incorrect type in assignment (different address spaces)
    drivers/media/platform/fsl-viu.c:1440:21:    expected struct viu_reg *vr
    drivers/media/platform/fsl-viu.c:1440:21:    got struct viu_reg [noderef] <asn:2>*[assigned] viu_regs

Signed-off-by: Mauro Carvalho Chehab <mchehab@s-opensource.com>