spi/qspi: Add dual/quad read mode bit.

Add dual/quad read mode bit flag for the master controller.
These check will be used in the spi framework to determine
whether the master controller can do dual/quad read respectively.

Signed-off-by: Sourav Poddar <sourav.poddar@ti.com>
Signed-off-by: Mark Brown <broonie@linaro.org>