kernel: Move to Linux v5.1.8-openpower1

Powerpc related changes:

 powerpc/kexec: Fix loading of kernel + initramfs with kexec_file_load()
 powerpc/perf: Fix MMCRA corruption by bhrb_filter

Signed-off-by: Joel Stanley <joel@jms.id.au>
diff --git a/openpower/linux/0002-Release-OpenPower-kernel.patch b/openpower/linux/0002-Release-OpenPower-kernel.patch
index aa646f3..3d6ede6 100644
--- a/openpower/linux/0002-Release-OpenPower-kernel.patch
+++ b/openpower/linux/0002-Release-OpenPower-kernel.patch
@@ -1,6 +1,6 @@
 From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
 From: Joel Stanley <joel@jms.id.au>
-Date: Mon, 3 Jun 2019 17:10:28 +0930
+Date: Tue, 11 Jun 2019 12:42:50 +0930
 Subject: [PATCH 2/2] Release OpenPower kernel
 
 Signed-off-by: Joel Stanley <joel@jms.id.au>
@@ -9,13 +9,13 @@
  1 file changed, 1 insertion(+), 1 deletion(-)
 
 diff --git a/Makefile b/Makefile
-index d8bdd2bb55dc..ec0598855d05 100644
+index 3027a0ce7a02..36f60a9cff05 100644
 --- a/Makefile
 +++ b/Makefile
 @@ -2,7 +2,7 @@
  VERSION = 5
  PATCHLEVEL = 1
- SUBLEVEL = 6
+ SUBLEVEL = 8
 -EXTRAVERSION =
 +EXTRAVERSION = -openpower1
  NAME = Shy Crocodile