tests: kernel: profiling: Fix _sys_soc_suspend logic

Call k_thread_foreach only once from _sys_soc_suspend()
otherwise it will flood the console with stack dumps. As per
the test implementation, the one time call happens through
test_call_stacks_analyze_idle test case.

Also removed the the stack size comparision logic from
thread_callback() as the actual size allocated could be
different from what is requested based on the Kconfig option
CONFIG_MPU_REQUIRES_POWER_OF_TWO_ALIGNMENT

Fixes Issue #7858

Signed-off-by: Ramakrishna Pallala <ramakrishna.pallala@intel.com>