xhci: hsic: Handle spurious port connect detect interrupt

Spurious port connect detect interrupt is observed when device
connected over hsic is powered down. This invokes hub thread
to handle port change event when hsic controller driver is
getting unbind as a sequence of device shutdown. This results
in memory corruption in the core and controller driver. Since
hsic is a single port root hub, ignore port connect detect
interrupt when port is already connected.

CRs-Fixed: 663418
Change-Id: If16c7db3a2fdd4268c54c6945cb45525934526b2
Signed-off-by: Hemant Kumar <hemantk@codeaurora.org>