mtd: move NAND files into a raw/ subdirectory

NAND flavors, like serial and parallel, have a lot in common and would
benefit to share code. Let's move raw (parallel) NAND specific code in a
raw/ subdirectory, to ease the addition of a core file in nand/ and the
introduction of a spi/ subdirectory specific to SPI NANDs.

Signed-off-by: Miquel Raynal <miquel.raynal@bootlin.com>
diff --git a/Makefile b/Makefile
index e38966e..807e803 100644
--- a/Makefile
+++ b/Makefile
@@ -689,7 +689,7 @@
 libs-y += drivers/gpio/
 libs-y += drivers/i2c/
 libs-y += drivers/mtd/
-libs-$(CONFIG_CMD_NAND) += drivers/mtd/nand/
+libs-$(CONFIG_CMD_NAND) += drivers/mtd/nand/raw/
 libs-y += drivers/mtd/onenand/
 libs-$(CONFIG_CMD_UBI) += drivers/mtd/ubi/
 libs-y += drivers/mtd/spi/