lxd/instance/qemu: Switch TPM mode to CRB
lxd/instance/qemu: Switch TPM mode to CRB

CRB mode is apparently faster than TIS and since we don't need 1.2 mode
(we only run in 2.0), TIS doesn't provide anything of value.

Signed-off-by: Stéphane Graber <089afc6d81f66f1168a9849e15660feae286e024@ubuntu.com>

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