mtd: fsl-quadspi: Remove the driver as it was replaced by spi-fsl-qspi.c

There's a new driver using the SPI memory interface of the SPI framework
at spi/spi-fsl-qspi.c, which can be used together with m25p80.c to
replace the functionality of this SPI NOR driver.

The new driver is already in use and this code is not compiled anymore,
so let's remove it.
Signed-off-by: Frieder Schrempf <frieder.schrempf@kontron.de>
Acked-by: Han Xu <han.xu@nxp.com>
Tested-by: Han Xu <han.xu@nxp.com>
Acked-by: Boris Brezillon <bbrezillon@kernel.org>
Signed-off-by: Mark Brown <broonie@kernel.org>