tpm: lookup cancel path under tpm device class

tpm: lookup cancel path under tpm device class

Since Linux commit 313d21eeab9282e, tpm devices have their own device
class "tpm" and the cancel path must be looked up under
/sys/class/tpm/ instead of /sys/class/misc/.

Signed-off-by: Marc-André Lureau <[email protected]>
Reviewed-by: Stefan Berger <[email protected]>
Signed-off-by: Stefan Berger <[email protected]>