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 SIMPLE_DEV_PM_OPS are only used when
the CONFIG_PM_SLEEP is enabled.

drivers/mmc/host/atmel-mci.c:2509:12: warning: 'atmci_suspend' defined but not used [-Wunused-function]
drivers/mmc/host/atmel-mci.c:2539:12: warning: 'atmci_resume' defined but not used [-Wunused-function]
Signed-off-by: NJingoo Han <jg1.han@samsung.com>
Acked-by: NLudovic Desroches <ludovic.desroches@atmel.com>
Signed-off-by: NChris Ball <cjb@laptop.org>