usb: musb: da8xx: fix babble condition handling

When babble condition happens, the musb controller might automatically
turns off VBUS. On DA8xx platform, the controller generates drvvbus
interrupt for turning off VBUS along with the babble interrupt.

In this case, we should handle the babble interrupt first and recover
from the babble condition.

This change ignores the drvvbus interrupt if babble interrupt is also
generated at the same time, so the babble recovery routine works
properly.

Cc: stable@vger.kernel.org # v3.16+
Signed-off-by: Bin Liu <b-liu@ti.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>