[boringssl] Depend on libcrypto from ssl_test

ssl_test depends on some libcrypto functions directly, so it should have
a dep on it. Previously it happened to work because libssl has a
non-public dep on libcrypto, but that shouldn't be enough.

Change-Id: I800c7d53047464234cd35646709ad7bc5867684b
diff --git a/BUILD.gn b/BUILD.gn
index a11fcf2..fc865f0 100644
--- a/BUILD.gn
+++ b/BUILD.gn
@@ -193,6 +193,7 @@
   sources = ssl_test_sources + test_support_sources
   configs += [ ":test_config" ]
   deps = [
+    ":crypto",
     ":ssl",
     "//third_party/gtest",
   ]