external/boringssl: Sync to a63d0ad40dd621d5b9472dc9f1756692f969451e.

This includes the following changes:

https://boringssl.googlesource.com/boringssl/+log/9f0e7cb314ae64234b928fd379381ae9760a9a5f..a63d0ad40dd621d5b9472dc9f1756692f969451e

Test: BoringSSL CTS Presubmits.
Change-Id: I283b7d8f01ceef3becb152708b65894c717e3680
diff --git a/src/include/openssl/cpu.h b/src/include/openssl/cpu.h
index dd95ddc..bb847f9 100644
--- a/src/include/openssl/cpu.h
+++ b/src/include/openssl/cpu.h
@@ -86,7 +86,8 @@
 //     Bit 11 is used to indicate AMD XOP support, not SDBG
 //   Index 2:
 //     EBX for CPUID where EAX = 7
-//   Index 3 is set to zero.
+//   Index 3:
+//     ECX for CPUID where EAX = 7
 //
 // Note: the CPUID bits are pre-adjusted for the OSXSAVE bit and the YMM and XMM
 // bits in XCR0, so it is not necessary to check those.