usb: musb: Use shared irq

In the DA8xx, USB and CPPI 4.1 are sharing the same interrupt line.
Update the driver to request a shared irq.

Signed-off-by: Alexandre Bailon <abailon@baylibre.com>
Signed-off-by: Bin Liu <b-liu@ti.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>