OpenSSL: Fix EAP-TLS connection failure in Android

OpenSSL: Fix EAP-TLS connection failure in Android

In Android, the client private key is stored in the keystore engine and
the code depends on OPENSSL_NO_ENGINE defined in BoringSSL to load the
private key.

Commit 400b89162294 ("OpenSSL: Use pkcs11-provider when
OPENSSL_NO_ENGINE is defined" broke the logic to load the client private
key in Android which resulted in EAP-TLS connection failure. With this
change pkcs11-provider is used when OPENSSL_NO_ENGINE is defined.

Fix the issue by adding conditional compilation check for Android
platform to avoid using Provider API.

Fixes: 400b89162294 ("OpenSSL: Use pkcs11-provider when OPENSSL_NO_ENGINE is defined")
Signed-off-by: sunilravi <sunilravi@google.com>