usb: xhci-msm-hsic: handle pwr event irq during lpm

Glitch on hsic lines can cause power event irq when controller
is suspended. Acknowledge the interrupt after turning on the
clocks if controller is suspended.

Change-Id: I2983e5d3670d3a704d217c41ffadbd9b7237619f
Signed-off-by: Vamsi Krishna <vskrishn@codeaurora.org>