spi: spi-zynq-qspi: Add description for 2 missing attributes/parameters

spi: spi-zynq-qspi: Add description for 2 missing attributes/parameters

Fixes the following W=1 kernel build warning(s):

 drivers/spi/spi-zynq-qspi.c:143: warning: Function parameter or member 'dev' not described in 'zynq_qspi'
 drivers/spi/spi-zynq-qspi.c:334: warning: Function parameter or member 'spi' not described in 'zynq_qspi_config_op'
 drivers/spi/spi-zynq-qspi.c:334: warning: Excess function parameter 'qspi' description in 'zynq_qspi_config_op'

Signed-off-by: Lee Jones <lee.jones@linaro.org>
Reviewed-by: Michal Simek <michal.simek@xilinx.com>
Cc: Sureshkumar Relli <nagasure@xilinx.com>
Link: https://lore.kernel.org/r/20200717135424.2442271-10-lee.jones@linaro.org
Signed-off-by: Mark Brown <broonie@kernel.org>