fix(marvell): upgrade crypto++ version

Bump to v8.7. The current version produces deprecation errors on newer
versions of gcc (available with Ubuntu Jammy).

Signed-off-by: Boyan Karatotev <boyan.karatotev@arm.com>
Change-Id: I16ed7b26bde3ea78d99005cb5505446ddde8e9ea
diff --git a/group/tf-l1-build-plat/a3700-default:nil b/group/tf-l1-build-plat/a3700-default:nil
index 843e8e0..06f4a3f 100644
--- a/group/tf-l1-build-plat/a3700-default:nil
+++ b/group/tf-l1-build-plat/a3700-default:nil
@@ -33,7 +33,7 @@
 
 	if [ ! -d "cryptopp" ]; then
 		saveas="cryptopp.zip" \
-			url="$tfa_downloads/cryptopp/cryptopp565.zip" \
+			url="$tfa_downloads/cryptopp/cryptopp870.zip" \
 			fetch_file
 
 		unzip -d cryptopp "cryptopp.zip"