arch/riscv: disable excess harts before picking main boot hart

Harts with id greater than or equal to CONFIG_NR_CPUS need to be
disabled.  But the kernel can pick any hart as the main hart.  So,
before picking the main hart, the kernel must disable harts with ids
greater than or equal to CONFIG_NR_CPUS.

Signed-off-by: Xiang Wang <merle@hardenedlinux.org>
Reviewed-by: Palmer Dabbelt <palmer@sifive.com>
Reviewed-by: Anup Patel <anup.patel@wdc.com>
[paul.walmsley@sifive.com: updated to apply; cleaned up patch
 description]
Signed-off-by: Paul Walmsley <paul.walmsley@sifive.com>

arch/riscv/kernel/head.S

@@ -63,6 +63,11 @@ _start_kernel:
 	li t0, SR_FS
 	csrc CSR_SSTATUS, t0
 
+#ifdef CONFIG_SMP
+	li t0, CONFIG_NR_CPUS
+	bgeu a0, t0, .Lsecondary_park
+#endif
+
 	/* Pick one hart to run the main boot sequence */
 	la a3, hart_lottery
 	li a2, 1
@@ -154,9 +159,6 @@ relocate:
 
 .Lsecondary_start:
 #ifdef CONFIG_SMP
-	li a1, CONFIG_NR_CPUS
-	bgeu a0, a1, .Lsecondary_park
-
 	/* Set trap vector to spin forever to help debug */
 	la a3, .Lsecondary_park
 	csrw CSR_STVEC, a3