tpm: Fix possible buffer overflow in PKDECRYPT

* tpm2d/tpm2.c (tpm2_ecc_decrypt): Bail out on too long CIPHERTEXT.
(tpm2_rsa_decrypt): Ditto.

Cherry pick master commit of:
93fa34d9a346020355cd51d54102d30d4f177323

• GnuPG-bug-id: T8045
• Co-authored-by: NIIBE Yutaka <gniibe@fsij.org>
• Reported-by: OpenAI Security Research