common: Drop flash.h from common header

Move this uncommon header out of the common header.

Fix up some style problems in flash.h while we are here.

Signed-off-by: Simon Glass <sjg@chromium.org>
diff --git a/drivers/fastboot/fb_command.c b/drivers/fastboot/fb_command.c
index 3c4acfe..49f6a61 100644
--- a/drivers/fastboot/fb_command.c
+++ b/drivers/fastboot/fb_command.c
@@ -10,6 +10,7 @@
 #include <fastboot-internal.h>
 #include <fb_mmc.h>
 #include <fb_nand.h>
+#include <flash.h>
 #include <part.h>
 #include <stdlib.h>