mtd: rawnand: qcom: Early structure initialization

Instead of allocating a structure on the stack with random data and then
expect the callee to perform the initialization (which is, in general,
error prone), prefer zeroing the structure explicitly at allocation and
provide the already zeroed area, so no explicit memset operation is
needed. It is probably safer to do so, so we limit the timeframe when
dirty data could actually be accessed by mistake.

Signed-off-by: Miquel Raynal <miquel.raynal@bootlin.com>
Acked-by: Manivannan Sadhasivam <mani@kernel.org>
Reviewed-by: Tudor Ambarus <tudor.ambarus@linaro.org>
Link: https://lore.kernel.org/linux-mtd/20230716144612.32132-8-miquel.raynal@bootlin.com