mtd: spi-nor: Add support for Macronix mx66l1g45g spi flash

These modules are used on the OpenPOWER Witherspoon systems to hold
the POWER9 host firmware image. The SPI_NOR_DUAL_READ flags is added
for the Aspeed SoCs which do not support QUAD reads.

Signed-off-by: Cédric Le Goater <clg@kaod.org>
Reviewed-by: Marek Vasut <marek.vasut@gmail.com>
Signed-off-by: Cyrille Pitchen <cyrille.pitchen@wedev4u.fr>