tpm: change tpm_crb to only call tpm_chip_unregister()

The "API promise" from framewor is ought to be such that chip
is not assumed to free chip itself.

Signed-off-by: Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com>
tpm: do not call tpm_chip_free() after tpm_chip_unregister()

tpm_chip_free() should not be called after tpm_chip_unregister()
as the tpm module should take that into concern after call to
tpm_chip_unregister().

Signed-off-by: Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com>