usb: gadget: Fix USB wake IRQ to be edge triggered

This patch fixes a possible interrupt storm condition by
the USB wake IRQ, which can cause a dog timeout crash.

The USB wake IRQ detects USB bus suspend on USB D+ line.
This can be done by a rising edge triggered interrupt,
rather than level triggered interrupt.

Change-Id: Ia5451c3847285d38dde893856680a011674bd1e3
Signed-off-by: Amit Blay <ablay@codeaurora.org>