App: Update test thread stack configuration

Remove user provided memory for stack used by test main thread.

This enables usage of FreeRTOS on the non-secure side to run the tests.
FreeRTOS requires that memory for thread control block and stack is
either user provided or provided by the system (cannot be mixed).

Signed-off-by: Robert Rostohar <Robert.Rostohar@arm.com>
Change-Id: I43ffd914d765bbda89dd10cd2bfa83fcb2be7791
2 files changed