mtd: spi-nor: Convert cadence-quadspi to use spi-mem framework

Move cadence-quadspi driver to use spi-mem framework. This is required
to make the driver support for SPI NAND flashes in future.

Driver is feature compliant with existing SPI NOR version.

Signed-off-by: Ramuthevar Vadivel Murugan <vadivel.muruganx.ramuthevar@linux.intel.com>
Signed-off-by: Vignesh Raghavendra <vigneshr@ti.com>
Reviewed-by: Tudor Ambarus <tudor.ambarus@microchip.com>
Acked-by: Tudor Ambarus <tudor.ambarus@microchip.com>
Link: https://lore.kernel.org/r/20200601070444.16923-8-vigneshr@ti.com
Signed-off-by: Mark Brown <broonie@kernel.org>