Switch another low-level function to spans.

Get this out of the way for the various TLS 1.3 secrets to use spans.

Change-Id: Ia6c3fa4b35ecfad721af665f54bde5ab16baf7ca
Reviewed-on: https://boringssl-review.googlesource.com/c/boringssl/+/37126
Commit-Queue: Steven Valdez <svaldez@google.com>
Reviewed-by: Steven Valdez <svaldez@google.com>

ssl/internal.h

diff --git a/ssl/internal.h b/ssl/internal.h
index 621052f..e9b8201 100644
--- a/ssl/internal.h
+++ b/ssl/internal.h
@@ -1799,9 +1799,9 @@
 // SSLKEYLOGFILE functions.
 
 // ssl_log_secret logs |secret| with label |label|, if logging is enabled for
-// |ssl|. It returns one on success and zero on failure.
-int ssl_log_secret(const SSL *ssl, const char *label, const uint8_t *secret,
-                   size_t secret_len);
+// |ssl|. It returns true on success and false on failure.
+bool ssl_log_secret(const SSL *ssl, const char *label,
+                    Span<const uint8_t> secret);
 
 
 // ClientHello functions.