KVM: selftests: Fix build of rseq test

The KVM rseq test is failing to build in -next due to a commit merged
from the tip tree which adds a wrapper for sys_getcpu() to the rseq
kselftests, conflicting with the wrapper already included in the KVM
selftest:

rseq_test.c:48:13: error: conflicting types for 'sys_getcpu'
   48 | static void sys_getcpu(unsigned *cpu)
          |             ^~~~~~~~~~
In file included from rseq_test.c:23:
../rseq/rseq.c:82:12: note: previous definition of 'sys_getcpu' was here
   82 | static int sys_getcpu(unsigned *cpu, unsigned *node)
          |            ^~~~~~~~~~

Fix this by removing the local wrapper and moving the result check up to
the caller.

Fixes: 99babd04 ("selftests/rseq: Implement rseq numa node id field selftest")
Signed-off-by: Mark Brown <broonie@kernel.org>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Acked-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Link: https://lore.kernel.org/r/20230106-fix-kvm-rseq-build-v1-1-b704d9831d02@kernel.org

tools/testing/selftests/kvm/rseq_test.c

@@ -41,18 +41,6 @@ static void guest_code(void)
 		GUEST_SYNC(0);
 }
 
-/*
- * We have to perform direct system call for getcpu() because it's
- * not available until glic 2.29.
- */
-static void sys_getcpu(unsigned *cpu)
-{
-	int r;
-
-	r = syscall(__NR_getcpu, cpu, NULL, NULL);
-	TEST_ASSERT(!r, "getcpu failed, errno = %d (%s)", errno, strerror(errno));
-}
-
 static int next_cpu(int cpu)
 {
 	/*
@@ -249,7 +237,9 @@ int main(int argc, char *argv[])
 			 * across the seq_cnt reads.
 			 */
 			smp_rmb();
-			sys_getcpu(&cpu);
+			r = sys_getcpu(&cpu, NULL);
+			TEST_ASSERT(!r, "getcpu failed, errno = %d (%s)",
+				    errno, strerror(errno));
 			rseq_cpu = rseq_current_cpu_raw();
 			smp_rmb();
 		} while (snapshot != atomic_read(&seq_cnt));