mtd/nand:Fix wrong usage of is_blank() in fsl_ifc_run_command

mtd/nand:Fix wrong usage of is_blank() in fsl_ifc_run_command

Freescale IFC NAND Machine calculates ECC on 512byte sector and same is used in
fsl_ifc_run_command() during ECC status verification. Also this sector is passed
to is_blank() for blank checking. It is wrong at first place because
is_blank()'s implementation checks for Page size and OOB area size.
is_blank() should be called per page for main and OOB area verification.

Variables name are redefined to avoid confusion between buffer and ecc sector.

Signed-off-by: Poonam Aggrwal <poonam.aggrwal@freescale.com>
Signed-off-by: Prabhakar Kushwaha <prabhakar@freescale.com>
Signed-off-by: Scott Wood <scottwood@freescale.com>