Fix linking with libpayload

o Move flashbuses_to_text() to flashrom.c, it's not a cli function.
o Guard `!defined(HAVE_STRNLEN)`. This guard was introduced in
  23e10b87 (Add a bunch of new/tested stuff and various small
  changes 24) to support older BSDs. It's probably completely
  broken because HAVE_STRNLEN is presumably a GNU autotools
  thing. But we can't fix it without retesting these older BSDs.

Change-Id: I561135209b819361d125eeaeef9ff886d6bae987
Signed-off-by: Nico Huber <nico.huber@secunet.com>
Reviewed-on: https://review.coreboot.org/18738
Reviewed-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
Reviewed-by: David Hendricks <david.hendricks@gmail.com>
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
diff --git a/flashrom.c b/flashrom.c
index 838dfd0..379f75e 100644
--- a/flashrom.c
+++ b/flashrom.c
@@ -1163,6 +1163,39 @@
 	return 0;
 }
 
+/*
+ * Return a string corresponding to the bustype parameter.
+ * Memory is obtained with malloc() and must be freed with free() by the caller.
+ */
+char *flashbuses_to_text(enum chipbustype bustype)
+{
+	char *ret = calloc(1, 1);
+	/*
+	 * FIXME: Once all chipsets and flash chips have been updated, NONSPI
+	 * will cease to exist and should be eliminated here as well.
+	 */
+	if (bustype == BUS_NONSPI) {
+		ret = strcat_realloc(ret, "Non-SPI, ");
+	} else {
+		if (bustype & BUS_PARALLEL)
+			ret = strcat_realloc(ret, "Parallel, ");
+		if (bustype & BUS_LPC)
+			ret = strcat_realloc(ret, "LPC, ");
+		if (bustype & BUS_FWH)
+			ret = strcat_realloc(ret, "FWH, ");
+		if (bustype & BUS_SPI)
+			ret = strcat_realloc(ret, "SPI, ");
+		if (bustype & BUS_PROG)
+			ret = strcat_realloc(ret, "Programmer-specific, ");
+		if (bustype == BUS_NONE)
+			ret = strcat_realloc(ret, "None, ");
+	}
+	/* Kill last comma. */
+	ret[strlen(ret) - 2] = '\0';
+	ret = realloc(ret, strlen(ret) + 1);
+	return ret;
+}
+
 int probe_flash(struct registered_master *mst, int startchip, struct flashctx *flash, int force)
 {
 	const struct flashchip *chip;