usb: bam: Allow apps to wakeup using BAM IRQ

To allow VDD min, we need to put the APPs core into suspend
power collapse.  At the moment, the BAM IRQ is not labeled as
wakeable, so it will not be able to wake the apps. This fix will
allow the core exit VDD min.

Change-Id: I6ef4a53ce5b553ce98bc7537aa2076a511ffb87d
CRs-Fixed: 467747
Signed-off-by: Bar Weiner <bweiner@codeaurora.org>