RISC-V: hwprobe: There can only be one first

Only capture the first cpu_id in order for the comparison
below to be of any use.

Fixes: ea3de9c ("RISC-V: Add a syscall for HW probing")
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/20230426141333.10063-2-ajones@ventanamicro.com
Signed-off-by: Palmer Dabbelt <palmer@rivosinc.com>

Author: Andrew Jones

arch/riscv/kernel/sys_riscv.c

@@ -103,8 +103,10 @@ static void hwprobe_arch_id(struct riscv_hwprobe *pair,
 			break;
 		}
 
-		if (first)
+		if (first) {
 			id = cpu_id;
+			first = false;
+		}
 
 		/*
 		 * If there's a mismatch for the given set, return -1 in the