kernel: Move to Linux v5.4.18-openpower1

Signed-off-by: Trung Lê <trung.le@ruby-journal.com>
diff --git a/openpower/linux/0003-Release-OpenPower-kernel.patch b/openpower/linux/0003-Release-OpenPower-kernel.patch
index b9504bb..1121b1a 100644
--- a/openpower/linux/0003-Release-OpenPower-kernel.patch
+++ b/openpower/linux/0003-Release-OpenPower-kernel.patch
@@ -15,7 +15,7 @@
 @@ -2,7 +2,7 @@
  VERSION = 5
  PATCHLEVEL = 4
- SUBLEVEL = 16
+ SUBLEVEL = 18
 -EXTRAVERSION =
 +EXTRAVERSION = -openpower1
  NAME = Kleptomaniac Octopus