tpm/tpm_tis: Add missing ifdef CONFIG_ACPI for pnp_acpi_device

This fixes a build failure if CONFIG_PNP is set but CONFIG_ACPI is not:
drivers/char/tpm/tpm_tis.c: In function ?tpm_tis_pnp_init?:
drivers/char/tpm/tpm_tis.c:912:45: error: invalid type argument of
?->? (have ?int?)
   acpi_dev_handle = pnp_acpi_device(pnp_dev)->handle;

If CONFIG_PNPACPI is not set pnp_acpi_device is defined as 0 and thus
accesing the handle is not possible.

Fixes: 0dc55365 ("tpm: fix raciness of PPI interface lookup")
Reported-by: Jim Davis <jim.epost@gmail.com>
Signed-off-by: Peter Huewe <peterhuewe@gmx.de>
Signed-off-by: James Morris <james.l.morris@oracle.com>