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/mtd/cfi_flash.c b/drivers/mtd/cfi_flash.c
index 4ce183b..036cf0b 100644
--- a/drivers/mtd/cfi_flash.c
+++ b/drivers/mtd/cfi_flash.c
@@ -22,6 +22,7 @@
 #include <env.h>
 #include <errno.h>
 #include <fdt_support.h>
+#include <flash.h>
 #include <irq_func.h>
 #include <asm/processor.h>
 #include <asm/io.h>