RISC-V: properly determine hardware caps

On the Hifive-U platform, cpu 0 is a masked cpu with less capabilities
than the other cpus.  Ignore it for the purpose of determining the
hardware capabilities of the system.
Signed-off-by: Andreas Schwab <schwab@suse.de>
Signed-off-by: Palmer Dabbelt <palmer@sifive.com>

arch/riscv/kernel/cpufeature.c

@@ -28,7 +28,7 @@ bool has_fpu __read_mostly;
 
 void riscv_fill_hwcap(void)
 {
-	struct device_node *node;
+	struct device_node *node = NULL;
 	const char *isa;
 	size_t i;
 	static unsigned long isa2hwcap[256] = {0};
@@ -44,9 +44,11 @@ void riscv_fill_hwcap(void)
 
 	/*
 	 * We don't support running Linux on hertergenous ISA systems.  For
-	 * now, we just check the ISA of the first processor.
+	 * now, we just check the ISA of the first "okay" processor.
 	 */
-	node = of_find_node_by_type(NULL, "cpu");
+	while ((node = of_find_node_by_type(node, "cpu")))
+		if (riscv_of_processor_hartid(node) >= 0)
+			break;
 	if (!node) {
 		pr_warning("Unable to find \"cpu\" devicetree entry");
 		return;