USB: xhci: rework xhci_print_ir_set() to get ir set from xhci itself

xhci->ir_set points to __iomem region, but xhci_print_ir_set accepts
plain struct xhci_intr_reg * causing multiple sparse warning at call
sites and inside the fucntion when we try to read that memory.

Instead of adding __iomem qualifier to the argument let's rework the
function so it itself gets needed register set from xhci and prints
it.

Signed-off-by: Dmitry Torokhov <dtor@vmware.com>
Signed-off-by: Sarah Sharp <sarah.a.sharp@linux.intel.com>