Check during SPI bitbang init that SPI bitbang master configuration is correct

Corresponding to flashrom svn r1092.

Signed-off-by: Carl-Daniel Hailfinger <c-d.hailfinger.devel.2006@gmx.net>
Acked-by: Michael Karcher <flashrom@mkarcher.dialup.fu-berlin.de>
diff --git a/flash.h b/flash.h
index c3302c4..3170efe 100644
--- a/flash.h
+++ b/flash.h
@@ -128,7 +128,7 @@
 void programmer_delay(int usecs);
 
 enum bitbang_spi_master_type {
-	BITBANG_SPI_DUMMY	/* remove as soon as there is a real entry */
+	BITBANG_SPI_INVALID	= 0, /* This must always be the first entry. */
 };
 
 struct bitbang_spi_master {