mtd: rawnand: meson: always use OOB bytes during write

mtd: rawnand: meson: always use OOB bytes during write

If 'oob_required' is not set by the caller (for example 'oobbuf' is NULL),
then driver doesn't copy OOB data from 'oob_poi' to special controller
structures, so zeroes will be written as OOB. But, generic raw NAND logic
in 'nand_base.c' already handles case when OOB is not required to write by
filling 'oob_poi' with 0xFF's. So let's remove 'oob_required' check to
always read 'oob_poi' data for OOB.

Kernel driver (drivers/mtd/nand/raw/meson_nand.c) works in the same way,
so need to keep same behaviour here.

Fixes: c2e8c4d09a7a ("mtd: rawnand: Meson NAND controller support")
Signed-off-by: Arseniy Krasnov <avkrasnov@salutedevices.com>
Reviewed-by: Michael Trimarchi <michael@amarulasolutions.com>