dmaengine: qcom: qcom-gpi-dma.h: fix all kernel-doc warnings

dmaengine: qcom: qcom-gpi-dma.h: fix all kernel-doc warnings

Add missing enum descriptions and spell one struct member correctly
to avoid kernel-doc warnings:

Warning: include/linux/dma/qcom-gpi-dma.h:15 Enum value 'SPI_TX' not
 described in enum 'spi_transfer_cmd'
Warning: include/linux/dma/qcom-gpi-dma.h:15 Enum value 'SPI_RX' not
 described in enum 'spi_transfer_cmd'
Warning: include/linux/dma/qcom-gpi-dma.h:15 Enum value 'SPI_DUPLEX' not
 described in enum 'spi_transfer_cmd'
Warning: include/linux/dma/qcom-gpi-dma.h:80 struct member 'multi_msg' not
 described in 'gpi_i2c_config'

Signed-off-by: Randy Dunlap <rdunlap@infradead.org>
Link: https://patch.msgid.link/20260301011203.3062658-1-rdunlap@infradead.org
Signed-off-by: Vinod Koul <vkoul@kernel.org>