tpm: return false from tpm_amd_is_rng_defective on non-x86 platforms

tpm_amd_is_rng_defective is for dealing with an issue related to the
AMD firmware TPM, so on non-x86 architectures just have it inline and
return false.

Cc: stable@vger.kernel.org # v6.3+
Reported-by: Sachin Sant <sachinp@linux.ibm.com>
Reported-by: Aneesh Kumar K. V <aneesh.kumar@linux.ibm.com>
Closes: https://lore.kernel.org/lkml/99B81401-DB46-49B9-B321-CF832B50CAC3@linux.ibm.com/
Fixes: f1324bbc

 ("tpm: disable hwrng for fTPM on some AMD designs")
Signed-off-by: Jerry Snitselaar <jsnitsel@redhat.com>
Reviewed-by: Jarkko Sakkinen <jarkko@kernel.org>
Signed-off-by: Jarkko Sakkinen <jarkko@kernel.org>