dmaengine: sirf: Add CONFIG_PM_SLEEP to suspend/resume functions

Add CONFIG_PM_SLEEP to suspend/resume functions to fix the following
build warning when CONFIG_PM_SLEEP is not selected. This is because
sleep PM callbacks defined by SET_SYSTEM_SLEEP_PM_OPS are only used
when the CONFIG_PM_SLEEP is enabled.

drivers/dma/sirf-dma.c:838:12: warning: 'sirfsoc_dma_pm_suspend' defined but not used [-Wunused-function]
drivers/dma/sirf-dma.c:879:12: warning: 'sirfsoc_dma_pm_resume' defined but not used [-Wunused-function]

Signed-off-by: Jingoo Han <jg1.han@samsung.com>
Signed-off-by: Vinod Koul <vinod.koul@intel.com>