Add missing include for bssl::Span.

This broke compile of the fipsmodule `.cc.inc` files on their own, and
makes `crypto/fipsmodule/bcm.cc` order dependent.

Change-Id: I15fe6fe37bf6a24127d669c34c71f032f6e39279
Reviewed-on: https://boringssl-review.googlesource.com/c/boringssl/+/84927
Auto-Submit: Rudolf Polzer <rpolzer@google.com>
Commit-Queue: David Benjamin <davidben@google.com>
Reviewed-by: David Benjamin <davidben@google.com>

crypto/fipsmodule/cipher/cipher.cc.inc

diff --git a/crypto/fipsmodule/cipher/cipher.cc.inc b/crypto/fipsmodule/cipher/cipher.cc.inc
index ec4ede0..f6c534d 100644
--- a/crypto/fipsmodule/cipher/cipher.cc.inc
+++ b/crypto/fipsmodule/cipher/cipher.cc.inc
@@ -21,6 +21,7 @@
 #include <openssl/err.h>
 #include <openssl/mem.h>
 #include <openssl/nid.h>
+#include <openssl/span.h>
 
 #include "../../internal.h"
 #include "../service_indicator/internal.h"