Update QEMU, QEMUv8, HiKey620, HiKey960, Juno and FVP to kernel v4.19

HiKey960 is now properly supported by upstream kernel v4.19, so drop the
platform-specific fork and use the new tip of our multi-platform
linaro-swg/linux/optee branch (which was recently rebased onto v4.19).
While we're at it, also upgrade other platforms.

Change-Id: I77d03d71350808561dfff0c90a4a8307ce274d9a
Signed-off-by: Jerome Forissier <jerome.forissier@linaro.org>
diff --git a/hikey.xml b/hikey.xml
index 8f49eac..d284eb1 100644
--- a/hikey.xml
+++ b/hikey.xml
@@ -14,7 +14,7 @@
         </project>
 
         <!-- linaro-swg gits -->
-        <project path="linux"                name="linaro-swg/linux.git"                  revision="75065d7a22b08115477ae75b42139c5336e28293" />
+        <project path="linux"                name="linaro-swg/linux.git"                  revision="221a1acee8047ae65c2d5980e3a7c5f73362c59d" />
         <project path="optee_examples"       name="linaro-swg/optee_examples.git" />
         <project path="patches_hikey"        name="linaro-swg/patches_hikey.git"          revision="d9c07f0ac0ce5fe57d367be82b8673aae8e81e96" />