USB: musb: check if set_irq_wake succeded and remember it

Without it, in platforms that don't provide irq_chip.set_wake(),
like omap, musb will WARN() on driver removal.

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