spi: bcm-qspi: Fix BSPI QUAD and DUAL mode support when using flex mode

spi: bcm-qspi: Fix BSPI QUAD and DUAL mode support when using flex mode

Fix data transfer width settings based on DT field 'spi-rx-bus-width'
to configure BSPI in single, dual or quad mode by using data width
and not the command width.

Fixes: ee29e65903e2d ("spi: bcm-qspi: Implement the spi_mem interface")
Signed-off-by: Rayagonda Kokatanur <rayagonda.kokatanur@broadcom.com>
Link: https://lore.kernel.org/r/1565086070-28451-1-git-send-email-rayagonda.kokatanur@broadcom.com
Signed-off-by: Mark Brown <broonie@kernel.org>