xhci: hsic: Enable xhci irq after xhci memory initialization

Spurious port change interrupt is causing access to xhci
data structures from xhci_irq() which causes memory corruption.
Avoid this by enabling xhci irq right before enabling HSIC phy
drives idle state on to the bus.

CRs-Fixed: 669583
Change-Id: I35bf904859fda7ad41df8e40b86338395adf2099
Signed-off-by: Hemant Kumar <hemantk@codeaurora.org>