lib: sbi: Allow platform to influence cold boot HART selection

We add an optional cold_boot_allowed() platform callback which allows
platform support to decide which HARTs can do cold boot initialization.

If this platform callback is not available then any HART can do cold
boot initialization.

Signed-off-by: Anup Patel <apatel@ventanamicro.com>

lib/sbi/sbi_init.c

@@ -498,8 +498,11 @@ void __noreturn sbi_init(struct sbi_scratch *scratch)
 	 * HARTs which satisfy above condition.
 	 */
 
-	if (next_mode_supported && atomic_xchg(&coldboot_lottery, 1) == 0)
-		coldboot = true;
+	if (sbi_platform_cold_boot_allowed(plat, hartid)) {
+		if (next_mode_supported &&
+		    atomic_xchg(&coldboot_lottery, 1) == 0)
+			coldboot = true;
+	}
 
 	/*
 	 * Do platform specific nascent (very early) initialization so