RISC-V: hwprobe: Explicity check for -1 in vdso init

id_bitsmash is unsigned. We need to explicitly check for -1, rather
than use > 0.

Fixes: aa5af0aa90 ("RISC-V: Add hwprobe vDSO function and data")
Signed-off-by: Andrew Jones <ajones@ventanamicro.com>
Reviewed-by: Conor Dooley <conor.dooley@microchip.com>
Reviewed-by: Evan Green <evan@rivosinc.com>
Link: https://lore.kernel.org/r/20230426141333.10063-3-ajones@ventanamicro.com
Signed-off-by: Palmer Dabbelt <palmer@rivosinc.com>

arch/riscv/kernel/sys_riscv.c

@@ -282,7 +282,7 @@ static int __init init_hwprobe_vdso_data(void)
 	 * populated) or any value returns -1 (varies across CPUs), then the
 	 * vDSO should defer to the kernel for exotic cpu masks.
 	 */
-	avd->homogeneous_cpus = (id_bitsmash > 0);
+	avd->homogeneous_cpus = id_bitsmash != 0 && id_bitsmash != -1;
 	return 0;
 }