usb: xhci-msm-hsic: Do not disable power event irq

Commit 877e12 (usb: xhci-msm-hsic: Handle power event irq
properly) only enabled power event irq during controller
suspend. HSIC controller generates power event irq for
IN_L2_IRQ as a result of HSIC bus suspend. This interrupt
remains un-acknowledged to controller if host initiated
resume causes bus resume and controller suspend is aborted.
HSIC controller becomes unresponsive when bus is suspended
next time and power event irq is generated for IN_L2_IRQ.
Hence always acknowledge IN_L2_IRQ to controller by leaving
power event irq enabled all the time and block on IN_L2_IRQ
before finishing HSIC bus suspend. Also register for
OUT_L2_IRQ and acknowledge it as per the hardware programming
guide recommendation.

CRs-Fixed: 609856
Change-Id: Ifaa3113da1b3f256c9d9b3db130918afc15d266f
Signed-off-by: Hemant Kumar <hemantk@codeaurora.org>