tpm: drop tpm_atmel specific fields from tpm_vendor_specific

Introduced a private struct tpm_atmel_priv that contains the variables
have_region and region_size that were previously located in struct
tpm_vendor_specific. These fields were only used by tpm_atmel.

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