dmaengine: fsl-edma: correct max_segment_size setting

Correcting the previous setting of 0x3fff to the actual value of 0x7fff.

Introduced new macro 'EDMA_TCD_ITER_MASK' for improved code clarity and
utilization of FIELD_GET to obtain the accurate maximum value.

Cc: stable@vger.kernel.org
Fixes: e0674853

 ("dmaengine: fsl-edma: support edma memcpy")
Signed-off-by: Frank Li <Frank.Li@nxp.com>
Link: https://lore.kernel.org/r/20240207194733.2112870-1-Frank.Li@nxp.com
Signed-off-by: Vinod Koul <vkoul@kernel.org>