Fix dependency (`requires` attribute) issue

The folder restructuring needed to support TF-M in Mbed OS caused Mbed
PSA services to be moved one folder under `FEATURE_PSA` but the `requires`
attribute was missing which is needed to include Mbed  PSA services.
This was causing build issue while building Mbed OS in baremetal mode.

Signed-off-by: Devaraj Ranganna <devaraj.ranganna@arm.com>

TESTS/configs/baremetal.json

@@ -6,6 +6,7 @@
         "utest",
         "unity",
         "psa",
+        "psa-services",
         "mbed-crypto",
         "mbedtls",
         "psa-compliance-framework",