Set default refspec value as NULL for dependency repos

TF-M dependency versions can be automatically parsed by CI scriptsg from
CMake system now. So keep default refspec value as NULL to use the TF-M
specified dependency version by default.

Signed-off-by: Xinyu Zhang <xinyu.zhang@arm.com>
Change-Id: I91c4ed7f5a4effb154054f8aeb43f6dccf0ecd9b
diff --git a/tf-m-cppcheck.yaml b/tf-m-cppcheck.yaml
index 71e2e70..e78bc1e 100644
--- a/tf-m-cppcheck.yaml
+++ b/tf-m-cppcheck.yaml
@@ -53,7 +53,7 @@
           default: 'master'
       - string:
           name: 'MBEDTLS_VERSION'
-          default: 'mbedtls-3.4.0'
+          default: ''
           description: |
             Specify which MBEDTLS version to use
             refs/heads/<branch_name> : Pick up latest HEAD on branch
@@ -64,7 +64,7 @@
           default: 'https://git.trustedfirmware.org/mirror/mbed-tls.git'
       - string:
           name: 'MCUBOOT_REFSPEC'
-          default: 'v1.10.0'
+          default: ''
           description: |
             Specify which MCUboot version to use
             refs/heads/<branch_name> : Pick up latest HEAD on branch
@@ -78,7 +78,7 @@
           default: 'https://git.trustedfirmware.org/TF-M/tf-m-tests.git'
       - string:
           name: 'TFM_TESTS_REFSPEC'
-          default: 'refs/heads/master'
+          default: ''
           description: |
             Specify which tf-m-tests version to use
             refs/heads/<branch_name> : Pick up latest HEAD on branch
@@ -89,7 +89,7 @@
           default: 'https://github.com/laurencelundblade/QCBOR.git'
       - string:
           name: 'QCBOR_VERSION'
-          default: '92d3f89030baff4af7be8396c563e6c8ef263622'
+          default: ''
           description: |
             Specify which QCBOR version to use
             refs/heads/<branch_name> : Pick up latest HEAD on branch