tpm: Fix compilation warning when CONFIG_PNP is not defined

The is_itpm() function is only accessed from a block surrounded by
#ifdef CONFIG_PNP. Therefore, also surround it with #ifdef CONFIG_PNP
and remove the #else branch causing the warning.

http://lxr.linux.no/#linux+v2.6.39/drivers/char/tpm/tpm_tis.c#L622



v2:
 - fixes a previous typo

Signed-off-by: Stefan Berger <stefanb@linux.vnet.ibm.com>
Reported-by: Randy Dunlap <rdunlap@xenotime.net>
Signed-off-by: James Morris <jmorris@namei.org>