Upgrade trusted-firmare-a to v2.6

Upgrade all platforms that use upstream TF-A to the latest v2.x version:
QEMU, FVP, HiKey, HiKey960, i.MX, Juno, Poplar, QEMUv8, RPi3, STM32MP1
and Synquacer.

Signed-off-by: Jerome Forissier <jerome@forissier.org>
Change-Id: I536be2a27d03569ad09467022ac80c11848e6feb
Acked-by: Jens Wiklander <jens.wiklander@linaro.org>
diff --git a/synquacer.xml b/synquacer.xml
index 67368d0..99a11c7 100644
--- a/synquacer.xml
+++ b/synquacer.xml
@@ -18,5 +18,5 @@
         <project path="edk2"                 name="tianocore/edk2.git"                    revision="21d9dc21f81828538af02ca9c2d86a36551b0771" />
         <project path="edk2-non-osi"         name="tianocore/edk2-non-osi.git"            revision="596043ffb61d5f74a9eb334eaa4df683fa975c92" />
         <project path="edk2-platforms"       name="tianocore/edk2-platforms.git"          revision="22d5f499135a0b43bfb723a983f93c3148d68494" />
-        <project path="trusted-firmware-a"   name="TF-A/trusted-firmware-a.git"           revision="refs/tags/v2.2" clone-depth="1" remote="tfo"/>
+        <project path="trusted-firmware-a"   name="TF-A/trusted-firmware-a.git"           revision="refs/tags/v2.6" clone-depth="1" remote="tfo"/>
 </manifest>