testsuite: Require atomic operations for c2y-if-decls-*

testsuite: Require atomic operations for c2y-if-decls-*

Since some of the c2y-if-decls tests use _Atomic, add a
requirement for target to support atomic operations on
int and long types.

This fixes spurious test link failures on pru-unknown-elf,
which lacks atomic ops.  The tests still pass on x86_64-linux-gnu.

gcc/testsuite/ChangeLog:

	* gcc.dg/c2y-if-decls-1.c: Require target that supports atomic
	operations on int and long types.
	* gcc.dg/c2y-if-decls-11.c: Ditto.
	* gcc.dg/c2y-if-decls-4.c: Ditto.
	* gcc.dg/c2y-if-decls-8.c: Ditto.

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