dmaengine: imx-sdma: Fix a build warning in sdma_runtime_resume function

Delete redundant variables 'i' and change disable_clk_ahb to
disable_clk_ipg to void following warning:
warning: unused variable 'i' [-Wunused-variable]
warning: label 'disable_clk_ipg' defined but not used

Fix commit 2da31cfd

("dmaengine: imx-sdma: Fix a hang when run dma test in imx8mq board")
Signed-off-by: Xiaolei Wang <xiaolei.wang@windriver.com>
Signed-off-by: Bruce Ashfield <bruce.ashfield@gmail.com>