linux-aspeed: Move to to 4.18.20

This includes security and bug fixes from the 4.18.20 stable release.

Note that 4.18 is now end of life for upstream security and bug fixes,
and systems should move to a supported release.

  https://lore.kernel.org/lkml/20181121103111.GA9112@kroah.com/

Change-Id: I4850c7b085634553270737e27a99f3401c89504b
Signed-off-by: Joel Stanley <joel@jms.id.au>
diff --git a/recipes-kernel/linux/linux-aspeed_git.bb b/recipes-kernel/linux/linux-aspeed_git.bb
index 364deff..8467063 100644
--- a/recipes-kernel/linux/linux-aspeed_git.bb
+++ b/recipes-kernel/linux/linux-aspeed_git.bb
@@ -1,6 +1,6 @@
 KBRANCH ?= "dev-4.18"
-LINUX_VERSION ?= "4.18.19"
+LINUX_VERSION ?= "4.18.20"
 
-SRCREV="62ccc3924eff37012bd0c227d8b7dc71188fc358"
+SRCREV="d608acfd4ac3fe17f3081bee8fcd4dcd896c2ffa"
 
 require linux-aspeed.inc