RISC-V: Fix testsuite regression due to recent IRA changes.

After IRA changes, atomic version will use one more register, but
non-atomic still use 2 registers, however this testcase isn't testing for
atomic feature, so I decide change the testcase to always use COUNT++
to test.

ChangeLog

gcc/testsuite/

Kito Cheng  <kito.cheng@sifive.com>

	* gcc.target/riscv/interrupt-2.c: Update testcase and expected output.

gcc/testsuite/ChangeLog

+2020-03-11  Kito Cheng  <kito.cheng@sifive.com>
+
+	* gcc.target/riscv/interrupt-2.c: Update testcase and expected output.
+
 2020-03-11  Richard Biener  <rguenther@suse.de>
 
 	* gcc.dg/torture/20200311-1.c: New testcase.

gcc/testsuite/gcc.target/riscv/interrupt-2.c

@@ -8,10 +8,6 @@ foo2 (void)
   INTERRUPT_FLAG = 0;
 
   extern volatile int COUNTER;
-#ifdef __riscv_atomic
-  __atomic_fetch_add (&COUNTER, 1, __ATOMIC_RELAXED);
-#else
   COUNTER++;
-#endif
 }
 /* { dg-final { scan-assembler-times "s\[wd\]\ta\[0-7\],\[0-9\]+\\(sp\\)" 2 } } */