tpm: fix the rollback in tpm_chip_register()

Fixed the rollback and gave more self-documenting names for the
functions.

Fixes: d972b052 ("tpm: fix call order in tpm-chip.c")
Signed-off-by: Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com>
cc: stable@vger.kernel.org
Reviewed-by: Jason Gunthorpe <jgunthorpe@obsidianresearch.com>