dmaengine: fsl-edma: fix all kernel-doc warnings

dmaengine: fsl-edma: fix all kernel-doc warnings

Use the correct kernel-doc format and struct member names to eliminate
these kernel-doc warnings:

Warning: include/linux/platform_data/dma-mcf-edma.h:35 struct member
 'dma_channels' not described in 'mcf_edma_platform_data'
Warning: include/linux/platform_data/dma-mcf-edma.h:35 struct member
 'slave_map' not described in 'mcf_edma_platform_data'
Warning: include/linux/platform_data/dma-mcf-edma.h:35 struct member
 'slavecnt' not described in 'mcf_edma_platform_data'

Signed-off-by: Randy Dunlap <rdunlap@infradead.org>
Link: https://patch.msgid.link/20260226051220.548566-1-rdunlap@infradead.org
Signed-off-by: Vinod Koul <vkoul@kernel.org>