tpm: drop 'base' from struct tpm_vendor_specific

Dropped the field 'base' from struct tpm_vendor_specific and migrated
it to the private structures of tpm_atmel and tpm_nsc.

Signed-off-by: Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com>
Reviewed-by: Jason Gunthorpe <jgunthorpe@obsidianresearch.com>