dmaengine: sa11x0: Fix warning and compilation errors

The sa11x0_dma_resume conflicts between the dmaengine device_resume callback
and the dev_pm_ops resume implementation.

Also remove some unused variables at the same time.

Signed-off-by: Maxime Ripard <maxime.ripard@free-electrons.com>
Signed-off-by: Vinod Koul <vinod.koul@intel.com>