swtpm_setup: Fail --decryption or --allow-signing without --tpm2

The help screen states that --decryption and --allow-signing require
--tpm2. Enforce this now also when checking flag combination since
neither flags would have any effect for a TPM 1.2.

Signed-off-by: Stefan Berger <stefanb@linux.ibm.com>
1 file changed