mtd: spinand: winbond: Enable high-speed modes on w25n0xjw

w25n0xjw chips have a high-speed capability hidden in a configuration
register. Once enabled, dual/quad SDR reads may be performed at a much
higher frequency.

Implement the new ->configure_chip() hook for this purpose and configure
the SR4 register accordingly.

Signed-off-by: Miquel Raynal <miquel.raynal@bootlin.com>