trusted-firmware-a: set mbedtls git branch with SRCBRANCH_MBEDTLS

Enables building latest bleeding edge tf-a and mbedtls with
local.conf setup:

INHERIT += "poky-bleeding"
POKY_AUTOREV_RECIPES += "trusted-firmware-a"

SRCREV_mbedtls:pn-trusted-firmware-a = "AUTOINC"
SRCREV_tfa:pn-trusted-firmware-a = "AUTOINC"
SRCBRANCH:pn-trusted-firmware-a = "master"
SRCBRANCH_MBEDTLS:pn-trusted-firmware-a = "master"
LIC_FILES_CHKSUM:pn-trusted-firmware-a = "file://docs/license.rst;md5=1118e32884721c0be33267bd7ae11130"
BBMASK += "meta-arm/recipes-bsp/trusted-firmware-a/trusted-firmware-a_2.10.12.bb"
BBMASK += "meta-arm-bsp/recipes-bsp/trusted-firmware-a/trusted-firmware-a_2.11.0.bb"

This includes workarounds for poky-bleeding.bbclass which doesn't
work with multiple SRCREV variables, masking away
tf-a 2.10 and 2.11 recipes which cause recipe parsing problems
and only one recipe needed to build latest upstream master
branch to avoid 503 error codes from remote git server.

Signed-off-by: Mikko Rapeli <mikko.rapeli@linaro.org>
Signed-off-by: Jon Mason <jon.mason@arm.com>

meta-arm/recipes-bsp/trusted-firmware-a/trusted-firmware-a_2.12.1.bb

@@ -8,7 +8,8 @@ LIC_FILES_CHKSUM += "file://docs/license.rst;md5=83b7626b8c7a37263c6a58af8d19bee
 
 # in TF-A src, docs/getting_started/prerequisites.rst lists the expected version mbedtls
 # mbedtls-3.6.2
-SRC_URI_MBEDTLS = "git://github.com/ARMmbed/mbedtls.git;name=mbedtls;protocol=https;destsuffix=git/mbedtls;branch=mbedtls-3.6"
+SRCBRANCH_MBEDTLS = "mbedtls-3.6"
+SRC_URI_MBEDTLS = "git://github.com/ARMmbed/mbedtls.git;name=mbedtls;protocol=https;destsuffix=git/mbedtls;branch=${SRCBRANCH_MBEDTLS}"
 SRCREV_mbedtls = "107ea89daaefb9867ea9121002fbbdf926780e98"
 
 LIC_FILES_CHKSUM_MBEDTLS = "file://mbedtls/LICENSE;md5=379d5819937a6c2f1ef1630d341e026d"