spi: spi-zynqmp-gqspi: Fix kernel-doc warnings

Document zynqmp_qspi ctrl and op_lock member description. It also adds
return documentation for 'zynqmp_qspi_setuprxdma' and zynqmp_qspi_read_op.

Fixes below kernel-doc warnings-

spi-zynqmp-gqspi.c:178: warning: Function parameter or member 'ctlr' not
described in 'zynqmp_qspi'
spi-zynqmp-gqspi.c:178: warning: Function parameter or member 'op_lock'
not described in 'zynqmp_qspi'

spi-zynqmp-gqspi.c:737: warning: No description found for return value of
'zynqmp_qspi_setuprxdma'
spi-zynqmp-gqspi.c:822: warning: No description found for return value of
'zynqmp_qspi_read_op'

Signed-off-by: Michal Simek <michal.simek@amd.com>
Signed-off-by: Amit Kumar Mahapatra <amit.kumar-mahapatra@amd.com>
Link: https://lore.kernel.org/r/20221011062040.12116-2-amit.kumar-mahapatra@amd.com


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