ARM: dts: msm: Update USB suspend enable flag

The "qcom,suspend_event_enable" property has been removed
as it has been repurposed to enable support for USB bus
suspend. Remove the only instance of this property found in
MDM9630 from the ssusb device and add its replacement
"snps,bus-suspend-enable" in the dwc3 child.

Change-Id: I1745c551aa21126bf3efcbea1e2f3446db5491f4
Signed-off-by: Jack Pham <jackp@codeaurora.org>