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/poplar.xml b/poplar.xml
index cbb9514..e3177dd 100644
--- a/poplar.xml
+++ b/poplar.xml
@@ -25,5 +25,5 @@
 
         <!-- Misc gits -->
         <project path="buildroot"            name="buildroot/buildroot.git"               revision="refs/tags/2021.11" clone-depth="1" />
-        <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>