tpm: Move tpm_buf code to include/linux/

Move tpm_buf code to common include/linux/tpm.h header so that it can
be reused via other subsystems like trusted keys etc.

Also rename trusted keys and asymmetric keys usage of TPM 1.x buffer
implementation to tpm1_buf to avoid any compilation errors.

Suggested-by: Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com>
Signed-off-by: Sumit Garg <sumit.garg@linaro.org>
Reviewed-by: Jerry Snitselaar <jsnitsel@redhat.com>
Reviewed-by: Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com>
Tested-by: Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com>
Signed-off-by: Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com>