tests: update CMocka to stable-1.1

CMocka stable-1.1 has some convenience bugfixes like vprint buffer
increase or leftover values log fix (funtion names display correctly
now.

Signed-off-by: Jakub Czapiga <jacz@semihalf.com>
Change-Id: I20ebd15324a21c17cccd2976ae9c3f86b040426d
Reviewed-on: https://review.coreboot.org/c/coreboot/+/63636
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Arthur Heymans <arthur@aheymans.xyz>

.gitmodules

@@ -48,6 +48,7 @@
 	path = 3rdparty/cmocka
 	url = ../cmocka.git
 	update = none
+	branch = stable-1.1
 [submodule "3rdparty/qc_blobs"]
 	path = 3rdparty/qc_blobs
 	url = ../qc_blobs.git