[dev.boringcrypto] crypto/tls: restore AES-GCM priority when BoringCrypto is enabled
[dev.boringcrypto] crypto/tls: restore AES-GCM priority when BoringCrypto is enabled

This patch used to be in crypto/internal/cipherhw.AESGCMSupport which
was removed from the tree. It was meant and documented to affect only
crypto/tls, so move the logic there.

Change-Id: I36ed4f08a5fe2abaab18907910899ae0297d1611
Reviewed-on: https://go-review.googlesource.com/114816
Run-TryBot: Filippo Valsorda <4f40cda291c5f9634e1affd3db44947af61f705c@golang.org>
TryBot-Result: Gobot Gobot <66cb808b70d30c07676d5e946fee83fd561249e5@golang.org>
Reviewed-by: Adam Langley <db68fba232b2c49ed3e9d3081df349dde7b61dfd@golang.org>

golang/go,nawawi/go,golang/go,nawawi/go,nawawi/go,golang/go,nawawi/go,nawawi/go,golang/go,golang/go,nawawi/go,nawawi/go,golang/go,golang/go,golang/go,nawawi/go