Migrate support to MbedTLS v2.26.0

Updated CI scripts to use latest release tagged MbedTLS repo
i.e. MbedTLS v2.26.0.

Release notes of Mbed TLSv2.26.0 are available here:
https://github.com/ARMmbed/mbedtls/releases/tag/v2.26.0

Change-Id: Ide402d96c717f7259168b1d5d3c0d2630a228a80
Signed-off-by: Manish V Badarkhe <Manish.Badarkhe@arm.com>
diff --git a/utils.sh b/utils.sh
index 5d3d6e0..b285087 100644
--- a/utils.sh
+++ b/utils.sh
@@ -336,12 +336,10 @@
 
 linaro_2001_release="${linaro_2001_release:-$tfa_downloads/linaro/20.01}"
 linaro_release="${linaro_release:-$linaro_2001_release}"
+mbedtls_version="${mbedtls_version:-2.26.0}"
 
 # mbedTLS archive public hosting available at github.com
-mbedtls_archive="${mbedtls_archive:-https://github.com/ARMmbed/mbedtls/archive/mbedtls-2.25.0.tar.gz}"
-# The tar file contains mbedtls-mbedtls-2.25.0 repo which holds the necessary
-# source files of mbedTLS project
-mbedtls_repo_name="${mbedtls_repo_name:-mbedtls-mbedtls-2.25.0}"
+mbedtls_archive="${mbedtls_archive:-https://github.com/ARMmbed/mbedtls/archive/mbedtls-${mbedtls_version}.tar.gz}"
 
 coverity_path="${coverity_path:-${nfs_volume}/tools/coverity/static-analysis/2020.06}"
 coverity_default_checkers=(