xhci-plat: Use USB glue driver device as sysdev

Currently xhci-plat's parent device is used as sysdev whereas USB driver
related page mapping is crated using xhci-plat's parent device's parent
device (i.e. USB glue driver device). This results into SMMU page fault
when XHCI controller is trying to access queued URB. Fix this issue by
checking sysdev->parent->parent->iommu_group availability and update
sysdev with USB glue driver device if iommu_group is set.

Change-Id: Iabf5b661b756c109663ad8b11a5a1dd9330c1171
Signed-off-by: Mayank Rana <mrana@codeaurora.org>