Depending on PM is not enough, because only PM_RUNTIME could be
selected. Fixes:

drivers/usb/musb/musb_dsps.c:703:12: warning: 'dsps_suspend' defined but not used [-Wunused-function]
drivers/usb/musb/musb_dsps.c:721:12: warning: 'dsps_resume' defined but not used [-Wunused-function]
Signed-off-by: NWolfram Sang <wsa@sang-engineering.com>
Signed-off-by: NFelipe Balbi <balbi@ti.com>