tests: benchmark: Mbed TLs: filter for posix arch

There is no point benchmarking on the posix architecture, and
how the test is now it just hungs. So let's filter it.

Signed-off-by: Alberto Escolar Piedras <[email protected]>

Author: aescolar

tests/benchmarks/mbedtls/testcase.yaml

@@ -6,6 +6,8 @@ common:
       - "Benchmark completed"
   timeout: 10
   tags: crypto
+  arch_exclude:
+    - posix
 tests:
   benchmark.crypto.mbedtls:
     filter: CONFIG_TEST_RANDOM_GENERATOR