selftests/seccomp: powerpc: Fix typo in macro variable name

A typo sneaked into the powerpc selftest. Fix the name so it builds again.

Fixes: 46138329 ("selftests/seccomp: powerpc: Fix seccomp return value testing")
Acked-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/lkml/87y2ix2895.fsf@mpe.ellerman.id.auSigned-off-by: Kees Cook <keescook@chromium.org>

tools/testing/selftests/seccomp/seccomp_bpf.c

@@ -1758,10 +1758,10 @@ TEST_F(TRACE_poke, getpid_runs_normally)
 		 * and the code is stored as a positive value.	\
 		 */						\
 		if (_result < 0) {				\
-			SYSCALL_RET(_regs) = -result;		\
+			SYSCALL_RET(_regs) = -_result;		\
 			(_regs).ccr |= 0x10000000;		\
 		} else {					\
-			SYSCALL_RET(_regs) = result;		\
+			SYSCALL_RET(_regs) = _result;		\
 			(_regs).ccr &= ~0x10000000;		\
 		}						\
 	} while (0)