spi: cadence-quadspi: Reset CMD_CTRL Reg on cmd r/w completion

If one leaves the CQSPI_REG_CMDCTRL in an unclean state this may cause
issues in future command reads. This issue came to light when some flash
reads in STIG mode were coming back dirty.

Signed-off-by: Dhruva Gole <d-gole@ti.com>
Link: https://lore.kernel.org/r/20230125081023.1573712-2-d-gole@ti.com


Signed-off-by: Mark Brown <broonie@kernel.org>