mtd: spi-nor: Fix quad enable for Spansion like flashes

The commit 7b678c69 ("mtd: spi-nor: Merge spansion Quad Enable
methods") forgot to actually set the QE bit in some cases. Thus this
breaks quad mode accesses to flashes which support readback of the
status register-2. Fix it.

Fixes: 7b678c69

 ("mtd: spi-nor: Merge spansion Quad Enable methods")
Signed-off-by: Michael Walle <michael@walle.cc>
Reviewed-by: Tudor Ambarus <tudor.ambarus@microchip.com>
Signed-off-by: Miquel Raynal <miquel.raynal@bootlin.com>