usb: dwc-msm: Handle power event IRQ with block reset

Power Event IRQ is enabled from DWC3 driver probe and different
USB low power state related events are masked/unmasked with
USB LPM functionality. USB block reset requires to turns
off USB clocks and re-enable it. Power event IRQ races with it
on turning off host mode and causing unclock register access from
this interrupt context. Fix this issue by disabling power event irq
before disabling USB clocks and re-enable after enabling USB clocks.

CRs-Fixed: 798693
Change-Id: Ie8f2cbb9bb94328662edf54cbe94ea8b9211e91e
Signed-off-by: Mayank Rana <mrana@codeaurora.org>