rmmod crashes the driver because tpm_chip_unregister() already sets ops
to NULL. This commit fixes the issue by moving tpm2_shutdown() to
tpm_chip_unregister(). This commit is also cleanup because it removes
duplicate code from tpm_crb and tpm_tis to the core.

Fixes: 4d3eac5e156a ("tpm: Provide strong locking for device removal")
Signed-off-by: NJarkko Sakkinen <jarkko.sakkinen@linux.intel.com>
Reviewed-by: NJason Gunthorpe <jgunthorpe@obsidianresearch.com>