mtd: eLBC NAND: remove elbc_fcm_ctrl->oob_poi

The eLBC NAND driver currently follows up each program/write operation with a
read-back of the page, in order to [ostensibly] fill in ECC data for the
caller. However, the page address used for this read is always -1, so the read
will never work correctly.  Remove this useless (and potentially problematic)
block of code.

Signed-off-by: Matthew L. Creech <mlcreech@gmail.com>
Signed-off-by: Artem Bityutskiy <dedekind1@gmail.com>