testsuite: Require atomic operations for hardbool-ai.c

testsuite: Require atomic operations for hardbool-ai.c

The test uses _Atomic int type, so add a filter to ensure the target
supports it.

This fixes a spurious test failure on pru-unknown-elf, which lacks
atomic ops.  The test still passes on x86_64-linux-gnu.

gcc/testsuite/ChangeLog:

	* gcc.dg/torture/hardbool-ai.c: Require target that supports
	atomic operations on int types.

Signed-off-by: Dimitar Dimitrov <dimitar@dinux.eu>