Fix everest build

Fix everest build following the merge of
9490. By the way removed an unnecessary
link of the everest lib to mbedtls test
executable. It comes through the mbedtls
library that gets it from the tfpsacrypto
library.

Signed-off-by: Ronald Cron <ronald.cron@arm.com>

tests/CMakeLists.txt

@@ -1,6 +1,5 @@
 set(libs
     ${mbedtls_target}
-    ${everest_target}
     ${CMAKE_THREAD_LIBS_INIT}
 )