arch/x86/bootblock_normal: Update to use fewer registers

- Move initialization of entry to later in main.
- Make boot_mode an unsigned char - no need to use int.
- Remove unnecessary variable filenames.
- Only get and try to boot fallback once.

Change-Id: I823092c60dd8c2de0a36ec7fdbba3e68f6b7567a
Test: compiled.
Signed-off-by: Martin Roth <martinroth@google.com>
Reviewed-on: https://review.coreboot.org/12574
Tested-by: build bot (Jenkins)
Reviewed-by: Patrick Georgi <pgeorgi@google.com>
Tested-by: Raptor Engineering Automated Test Stand <noreply@raptorengineeringinc.com>
Reviewed-by: Stefan Reinauer <stefan.reinauer@coreboot.org>

src/arch/x86/bootblock_normal.c

@@ -10,9 +10,9 @@ static const char *get_fallback(const char *stagelist) {
 
 static void main(unsigned long bist)
 {
-	unsigned long entry;
+	u8 boot_mode;
-	int boot_mode;
+	const char *default_filenames =
-	const char *default_filenames = "normal/romstage\0fallback/romstage";
+		"normal/romstage\0fallback/romstage";
 
 	if (boot_cpu()) {
 		bootblock_mainboard_init();
@@ -30,22 +30,22 @@ static void main(unsigned long bist)
 		boot_mode = boot_use_normal(cmos_read(RTC_BOOT_BYTE));
 	}
 
-	char *filenames = (char *)walkcbfs("coreboot-stages");
+	char *normal_candidate = (char *)walkcbfs("coreboot-stages");
-	if (!filenames) {
-		filenames = default_filenames;
-	}
-	char *normal_candidate = filenames;
 
-	if (boot_mode)
+	if (!normal_candidate)
+		normal_candidate = default_filenames;
+
+	unsigned long entry;
+
+	if (boot_mode) {
 		entry = findstage(normal_candidate);
-	else
+		if (entry)
-		entry = findstage(get_fallback(normal_candidate));
+			call(entry, bist);
+	}
 
-	if (entry) call(entry, bist);
-
-	/* run fallback if normal can't be found */
 	entry = findstage(get_fallback(normal_candidate));
-	if (entry) call(entry, bist);
+	if (entry)
+		call(entry, bist);
 
 	/* duh. we're stuck */
 	halt();