kernel: Move to Linux 4.13.8-openpower2

This replaces our existing non-upstream xhci fix with another
non-upstream xhci fix. It goes back to the original
usb_hcd_pci_shutdown() handler and instead performs a hardware reset of
the controller in xhci_shutdown().

Discussion of this change can be found here:
https://marc.info/?l=linux-usb&m=150853502520762&w=2

This fixes a particular issue on p9dsu, and after some testing does not
appear to regress on other platforms.

Signed-off-by: Samuel Mendoza-Jonas <sam@mendozajonas.com>
diff --git a/openpower/linux/0005-Release-OpenPower-kernel.patch b/openpower/linux/0005-Release-OpenPower-kernel.patch
index c4aab84..4d91515 100644
--- a/openpower/linux/0005-Release-OpenPower-kernel.patch
+++ b/openpower/linux/0005-Release-OpenPower-kernel.patch
@@ -9,7 +9,7 @@
  1 file changed, 1 insertion(+), 1 deletion(-)
 
 diff --git a/Makefile b/Makefile
-index 66ec023da822..41f1e259ce85 100644
+index 66ec023da822..4b8c4cb589ac 100644
 --- a/Makefile
 +++ b/Makefile
 @@ -1,7 +1,7 @@
@@ -17,7 +17,7 @@
  PATCHLEVEL = 13
  SUBLEVEL = 8
 -EXTRAVERSION =
-+EXTRAVERSION = -openpower1
++EXTRAVERSION = -openpower2
  NAME = Fearless Coyote
  
  # *DOCUMENTATION*