common: Drop linux/stringify.h from common header

Move this uncommon header out of the common header.

Signed-off-by: Simon Glass <sjg@chromium.org>
diff --git a/cmd/fastboot.c b/cmd/fastboot.c
index 4f35108..ad5c064 100644
--- a/cmd/fastboot.c
+++ b/cmd/fastboot.c
@@ -14,6 +14,7 @@
 #include <net.h>
 #include <usb.h>
 #include <watchdog.h>
+#include <linux/stringify.h>
 
 static int do_fastboot_udp(int argc, char *const argv[],
 			   uintptr_t buf_addr, size_t buf_size)