dmaengine: stm32-mdma: fix STM32_MDMA_CTBR_TSEL_MASK

This patch fixes STM32_MDMA_CTBR_TSEL_MASK, which is [5:0], not [7:0].

Fixes: a4ffb13c ("dmaengine: Add STM32 MDMA driver")
Signed-off-by: Amelie Delaunay <amelie.delaunay@foss.st.com>
Link: https://lore.kernel.org/r/20211220165827.1238097-1-amelie.delaunay@foss.st.com


Signed-off-by: Vinod Koul <vkoul@kernel.org>