xhci: Fix register save/restore order.

xhci: Fix register save/restore order.

The xHCI 1.0 spec errata released on June 13, 2011, changes the ordering
that the xHCI registers are saved and restored in.  It moves the
interrupt pending (IMAN) and interrupt control (IMOD) registers to be
saved and restored last.  I believe that's because the host controller
may attempt to fetch the event ring table when interrupts are
re-enabled.  Therefore we need to restore the event ring registers
before we re-enable interrupts.

This should be backported to kernels as old as 2.6.37, that contain the
commit 4c26c065e8970d0209da92240190d581a22547ca "USB: xHCI: PCI power
management implementation"

Signed-off-by: Sarah Sharp <sarah.a.sharp@linux.intel.com>
Tested-by: Elric Fu <elricfu1@gmail.com>
Cc: Andiry Xu <andiry.xu@amd.com>
Cc: stable@vger.kernel.org