linux-aspeed: Move to 5.4.21

This includes security and bug fixes from the 5.4.17, 5.4.18, 5.4.19,
5.4.20 and 5.4.21 stable releases.

Change-Id: I5b942278bbbb268595c999df22bed6a8a2798c29
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 b947839..5a99df6 100644
--- a/recipes-kernel/linux/linux-aspeed_git.bb
+++ b/recipes-kernel/linux/linux-aspeed_git.bb
@@ -1,6 +1,6 @@
 KBRANCH ?= "dev-5.4"
-LINUX_VERSION ?= "5.4.16"
+LINUX_VERSION ?= "5.4.21"
 
-SRCREV="86f83a82c7052073cba3db4549233e9c0641484b"
+SRCREV="3409ca6f2234aa37c2f54ca42aa6a3bde00a92c0"
 
 require linux-aspeed.inc