mtd: rawnand: Rename a NAND chip option

mtd: rawnand: Rename a NAND chip option

NAND controller drivers can set the NAND_USE_BOUNCE_BUFFER flag to a
chip 'option' field. With this flag, the core is responsible of
providing DMA-able buffers.

The current behavior is to not force the use of a bounce buffer when
the core thinks this is not needed. So in the end the name is a bit
misleading, because in theory we will always have a DMA buffer but in
practice it will not always be a bounce buffer.

Rename this flag NAND_USES_DMA to be more accurate.

Signed-off-by: Miquel Raynal <miquel.raynal@bootlin.com>
Reviewed-by: Boris Brezillon <boris.brezillon@collabora.com>
Link: https://lore.kernel.org/linux-mtd/20200507105241.14299-4-miquel.raynal@bootlin.com