dmaengine: ti: k3-udma-glue: fix channel enable functions

dmaengine: ti: k3-udma-glue: fix channel enable functions

Now the K3 UDMA glue layer enable functions perform RMW operation on UDMA
RX/TX RT_CTL registers to set EN bit and enable channel, which is
incorrect, because only EN bit has to be set in those registers to enable
channel (all other bits should be cleared 0).
More over, this causes issues when bootloader leaves UDMA channel RX/TX
RT_CTL registers in incorrect state - TDOWN bit set, for example. As
result, UDMA channel will just perform teardown right after it's enabled.

Hence, fix it by writing correct values (EN=1) directly in UDMA channel
RX/TX RT_CTL registers in k3_udma_glue_enable_tx/rx_chn() functions.

Fixes: d70241913413 ("dmaengine: ti: k3-udma: Add glue layer for non DMAengine users")
Signed-off-by: Grygorii Strashko <grygorii.strashko@ti.com>
Acked-by: Peter Ujfalusi <peter.ujfalusi@ti.com>
Link: https://lore.kernel.org/r/20200916120955.7963-1-grygorii.strashko@ti.com
Signed-off-by: Vinod Koul <vkoul@kernel.org>