Allow runtime configuration of "zero-delay" check

Define the new "-2" value for bootdelay to mean autoboot with no delay
and don't check for an abort key (while "0" value means do check).

Signed-off-by: Joe Hershberger <joe.hershberger@ni.com>

README

@@ -704,6 +704,8 @@ The following options need to be configured:
 - Boot Delay:	CONFIG_BOOTDELAY - in seconds
 		Delay before automatically booting the default image;
 		set to -1 to disable autoboot.
+		set to -2 to autoboot with no delay and not check for abort
+		(even when CONFIG_ZERO_BOOTDELAY_CHECK is defined).
 
 		See doc/README.autoboot for these options that
 		work with CONFIG_BOOTDELAY. None are required.

common/main.c

@@ -222,6 +222,7 @@ int abortboot(int bootdelay)
 #ifdef CONFIG_MENUPROMPT
 	printf(CONFIG_MENUPROMPT);
 #else
+	if (bootdelay >= 0)
 		printf("Hit any key to stop autoboot: %2d ", bootdelay);
 #endif
 
@@ -382,7 +383,7 @@ void main_loop (void)
 
 	debug ("### main_loop: bootcmd=\"%s\"\n", s ? s : "<UNDEFINED>");
 
-	if (bootdelay >= 0 && s && !abortboot (bootdelay)) {
+	if (bootdelay != -1 && s && !abortboot(bootdelay)) {
 # ifdef CONFIG_AUTOBOOT_KEYED
 		int prev = disable_ctrlc(1);	/* disable Control C checking */
 # endif