Simplify preprocessor logic in SignalCatchingOperationsTestCase.cpp
Simplify preprocessor logic in SignalCatchingOperationsTestCase.cpp

Without the change, compilation with toolchain based on GCC 7 results in
'warning: this use of "defined" may not be portable
[-Wexpansion-to-defined]'. "defined(...)" is actually not needed, as
undefined identifier will be treated as 0, which will cause the next
condition ("CONFIG_MAIN_THREAD_SIGNAL_ACTIONS >= 1") to be false anyway.
jasmin-j/distortos,jasmin-j/distortos,jasmin-j/distortos,CezaryGapinski/distortos,CezaryGapinski/distortos,jasmin-j/distortos,DISTORTEC/distortos,DISTORTEC/distortos,CezaryGapinski/distortos,DISTORTEC/distortos,DISTORTEC/distortos,CezaryGapinski/distortos,jasmin-j/distortos,CezaryGapinski/distortos