crypto: omap-aes-gcm - add missing .setauthsize hooks

GCM only permits certain tag lengths, so populate the .setauthsize
hooks which ensure that only permitted sizes are accepted by the
implementation.

Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
Reviewed-by: Tero Kristo <t-kristo@ti.com>
Tested-by: Tero Kristo <t-kristo@ti.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>