Revert "USB: musb: pm: don't rely fully on clock support"

This reverts commit 32d5dc95.

Needed to properly merge the musb changes that are in the
usb-next branch into Linus's tree.

Acked-by: Felipe Balbi <balbi@ti.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>