mtd: spinand: micron: Describe the SPI NAND device MT29F2G01ABAGD

Add the SPI NAND device MT29F2G01ABAGD series number, size and voltage
details as a comment.

Signed-off-by: Shivamurthy Shastri <sshivamurthy@micron.com>
Reviewed-by: Boris Brezillon <boris.brezillon@collabora.com>
Signed-off-by: Miquel Raynal <miquel.raynal@bootlin.com>
Link: https://lore.kernel.org/linux-mtd/20200311175735.2007-3-sshivamurthy@micron.com